Disposable, microwaveable containers having suitable food contact compatible olfactory properties and process for their manufacture

ABSTRACT

Low-odor microwaveable polypropylene/mica food contact articles are disclosed. The articles are prepared by low temperature processing and typically include odor-suppressing basic organic or inorganic compounds. Preferably, the articles are substantially free from C8 and C9 organic ketones associated with undesirable odors. Further improvements to the articles include crack-resistant embodiments with synergistic amounts of polyethylene and titanium dioxide.

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application is a non-provisional application based onU.S. Provisional Application Serial No. 60/078,923 filed Mar. 20, 1998of the same title, the priority of which is claimed.

BACKGROUND OF THE INVENTION

[0002] Filled polypropylene articles have been observed to exhibitundesirable odors, particularly upon heating. In this respect, see U.S.Pat. No. 5,023,286 to Abe et al., wherein phenolic antioxidants aresuggested to control the odor problem. Other polypropylene compositionsmay be found in U.S. Pat. Nos. 4,734,450 to Kawai et al.; U.S. Pat. No.5,045,369 to Kobayashi et al.; U.S. Pat. No. 5,300,747 of Simon; U.S.Pat. No. 5,439,628 of Huang and U.S. Pat. No. 4,933,526 of Fisher et al.

[0003] This invention relates to disposable, polypropylene/micamicrowaveable containers having suitable food contact compatibleolfactory properties including cups, trays, souffle dishes, lids,plates, bowls, and related articles of manufacture useful forpreparation, storage, delivery, and serving of food, wherein convenienceand low cost are of paramount importance. Nevertheless, suitable foodcontact compatible olfactory properties, appearance, and tactilecharacteristics of the plate, container, etc., are important forconsumer preference. The suitability of these disposable articles ofmanufacture for microwave cooking, or heating of food, has an importantplace in today's marketplace. Both the commercial and retail marketcomponents need an aesthetically pleasing microwaveable, disposable,rigid and strong container, plate, or cup, and related articles ofmanufacture which also have suitable food contact compatible olfactoryproperties.

[0004] These disposable microwaveable containers and plates exhibit amelting point of no less than about 250° F., the containers or platesbeing dimensionally stable and resistant to grease, sugar and water attemperatures up to at least 220° F. and exhibiting sufficient toughnessto be resistant to cutting by serrated polystyrene flatware and alsoexhibiting food contact compatible olfactory properties. The preferredcontainers and plates exhibit both suitable food contact compatibleolfactory properties and at least one micronodular surface on the foodcontact side of the container or plate.

SUMMARY OF THE INVENTION

[0005] Microwaveable, disposable, rigid and strong containers and plateshaving suitable food contact compatible olfactory properties have beenprepared. These disposable and microwaveable articles of manufactureexhibit (a) suitable food contact compatible olfactory properties; and(b) a melting point of not less than 250° F., suitably 250° F. to 330°F. In preferred embodiments these articles of manufacture exhibit amicronodular surface on the side coming in contact with food. Thesemicrowaveable, food contact compatible containers and plates aredimensionally stable and resistant to grease, sugar and water attemperatures of at least 220° F. and are of sufficient toughness to beresistant to cutting by serrated polystyrene flatware. The containersand plates of this invention answer a long felt need for products whichcan withstand the severe conditions of a microwave oven when commonfoods such as beans and pork, pancakes with syrup, pepperoni pizza, andbroccoli with cheese are microwaved during food cooking andreconstituting processes.

[0006] It has been found in accordance with the present invention thatpolypropylene/mica food contact articles such as bowls or plates exhibitsuitable olfactory characteristics when prepared by a low temperatureprocess and/or when prepared including a basic organic or inorganiccompound. There is provided in a first aspect of the present invention,a microwaveable, disposable food service article having food contactcompatible olfactory properties formed of a melt processedpolyolefin/mica composition wherein the composition includes from about40 to about 90% by weight of a polypropylene polymer and from about 10to about 50% by weight mica where the melt processed compositionexhibits low odor as characterized by a relative aroma intensity indexof less than about 1.6. Less than about 1.5 is more preferred and, as apractical matter, the lower limit of the relative aroma intensity indexfor the inventive composition is believed to be about 0.1.

[0007] Typically, the melt processed composition from which themicrowaveable article is formed also includes a basic organic orinorganic compound including the reaction product of an alkali metal oralkaline earth element with carbonates, phosphates, carboxylic acids aswell as alkali metal and alkaline earth element oxides, hydroxides, orsilicates and basic metal oxides including mixtures of silicone dioxidewith one or more of the following oxides: magnesium oxide, calciumoxide, barium oxide, and mixtures of the foregoing. More specifically,the basic organic or inorganic compound may be selected from the groupconsisting of: calcium carbonate, sodium carbonate, potassium carbonate,barium carbonate, aluminum oxide, sodium silicate, sodium borosilicate,magnesium oxide, strontium oxide, barium oxide, zeolites, sodiumcitrate, potassium citrate, calcium stearate, potassium stearate, sodiumphosphate, potassium phosphate, magnesium phosphate, mixtures ofsilicone dioxide with one or more of the following oxides: magnesiumoxide, calcium oxide, barium oxide, and mixtures of one or more of theabove. Furthermore, hydroxides of the metals and alkaline earth elementsrecited above may be utilized.

[0008] Where a basic inorganic odor suppressing compound is chosen,generally such compound is selected from the group consisting of calciumcarbonate, sodium carbonate, potassium carbonate, barium carbonate,aluminum oxide, sodium silicate, sodium borosilicate, magnesium oxide,strontium oxide, barium oxide, zeolites, sodium phosphate, potassiumphosphate, magnesium phosphate, mixtures of silicone dioxide with one ormore of the following oxides: magnesium oxide, calcium oxide, bariumoxide, and mixtures of one or more of the basic inorganic compounds setforth above. The amount of a basic inorganic compound is generally fromabout 2 to 20 weight percent, but is usually from about 5 to about 15weight percent of the article. Most preferably the basic inorganiccompound selected is calcium carbonate; typically present from about 5to about 20 weight percent.

[0009] Where an organic compound is chosen, it is typically selectedfrom the group consisting of sodium stearate, calcium stearate,potassium stearate, sodium citrate, potassium citrate, and mixtures ofthese where the amount of such compound is from about 0.5 to about 2.5weight percent of the article.

[0010] Typically, microwaveable articles produced in accordance with thepresent invention exhibit a relative aroma intensity index of less thanabout 1.0; preferably less than about 0.7; with a practical lower limitbeing 0.1 or so.

[0011] As shown below in connection with microwaveability testing, andsummarized in Table 20, competing commercial polystyrene type platescannot withstand the high temperatures generated in the microwave ovenduring food contact and either significantly warp or deform when theaforementioned food products were heated on them. Under the usualmicrowaving conditions with high grease content foods, the prior artplates tend to deform and flow to the point where parts of the platebecome adhered to the inside of the microwave oven. For disposableplates and containers, having suitable food contact olfactoryproperties, appearance and feel are important attributes. Themicronodular surface of the plates and containers of this inventionwhere mica and the basic inorganic compound or basic organic compoundare used in combination with polypropylene or polypropylene polyethylenecopolymers or blends tend to give these products the pleasingappearance, feel of stoneware or a pottery-like look and suitable foodcontact olfactory properties. Another significant property of thecontainers and plates of this invention is their cut resistance. Theserigid articles of manufacture are of sufficient toughness to beresistant to cutting by serrated polystyrene flatware. In normal usagethey are also resistant to cutting by regular metal flatware.

[0012] Whereas any microwaveable article may be produced in accordancewith the invention, most typically the article is a bowl or a platesuitable for serving food at a meal. The articles may be produced byinjection molding; however, preferred articles are thermoformed andinclude a micronodular food contact surface. Micronodular food contactsurfaces are produced by thermoforming a sheet into the article whichhas been extruded optionally with at least one matte roll and by vacuumthermoforming the sheet by applying vacuum opposite to the surface wherethe micronodular surface is desired. Most typically the micronodularsurface will have a surface gloss of less than about 35 at 75° asmeasured by TAPPI method T-480-OM 92. Articles also will typically havea Parker Roughness Value of at least about 12 microns.

[0013] While any suitable polypropylene polymer may be used, thepolypropylene polymers are preferably selected from the group consistingof isotactic polypropylene, and copolymers of propylene and ethylenewherein the ethylene moiety is less than about 10% of the units makingup the polymer, and mixtures thereof. Generally, such polymers have amelt flow index from about 0.3 to about 4, but most preferably thepolymer is isotactic polypropylene with a melt-flow index of about 1.5.In particularly preferred embodiments, the melt compounded compositionfrom which the resultant extruded sheet is formed into articles furtherincludes a polyethylene component and titanium dioxide. The polyethylenecomponent may be any suitable polyethylene such as HDPE, LDPE, MDPE,LLDPE or mixtures thereof.

[0014] The various polyethylene polymers referred to herein aredescribed at length in the Encyclopedia of Polymer Science & Engineering(2d Ed.), Vol. 6; pp: 383-522, Wiley 1986; the disclosure of which isincorporated herein by reference. HDPE refers to high densitypolyethylene which is substantially linear and has a density ofgenerally greater that 0.94 up to about 0.97 g/cc. LDPE refers to lowdensity polyethylene which is characterized by relatively long chainbranching and a density of about 0.912 to about 0.925 g/cc. LLDPE orlinear low density polyethylene is characterized by short chainbranching and a density of from about 0.92 to about 0.94 g/cc. Finally,intermediate density polyethylene (MDPE) is characterized by relativelylow branching and a density of from about 0.925 to about 0.94 g/cc.Unless otherwise indicated these terms have the above meaning throughoutthe description which follows.

[0015] The microwaveable articles according to the invention typicallyexhibit melting points from about 250 to about 330° F. and include micain amounts from about 20 to about 35 weight percent. Most preferablymica is present at about 30 weight percent.

[0016] It has been found that C8 and C9 organic ketones correlate wellwith or are associated with undesirable odors in polypropylene/micacompositions. Accordingly, it is preferred that articles in accordancewith the invention are substantially free from volatile C8 and C9organic ketones. In order to avoid undesirable odors, articles inaccordance with the invention are preferably prepared from a meltcompounded polyolefin mica composition which is prepared at a processmelt temperature of less than about 425° F.; with below about 400° F.being even more preferred. Optionally, the melt processedpolyolefin/mica composition is melt compounded in a nitrogen atmosphere.

[0017] In another aspect of the invention there is provided amicrowaveable, disposable food contact article having food contactcompatible olfactory properties formed of a melt processedpolyolefin/mica composition wherein said composition includes from about40 to about 90 percent by weight of a polypropylene polymer and fromabout 10 to about 50 percent by weight mica and a basic organic orinorganic odor suppressing compound including the reaction product of analkali metal or an alkaline earth element with carbonates, phosphates,carboxylic acids as well as alkali metal and alkaline earth elementoxides and silicates and basic metal oxides, including mixtures ofsilicone dioxides with one or more of the following oxides: magnesiumoxide, calcium oxide, barium oxide, and mixtures thereof.

[0018] Preferably the inventive articles are prepared from a meltcompounded polyolefin/mica composition prepared by way of a lowtemperature compounding process.

[0019] A preferred low temperature compounding process used forproducing polypropylene/mica melt compounded compositions including abasic odor suppressing agent having olfactory properties suitable forfood contact applications in accordance with the invention includes thesequential steps of: (a) preheating a polypropylene polymer whilemaintaining the polymer below a maximum temperature of about 350° F. andmore preferably below a maximum of about 260° F.; but suitably aboveabout 240° F.; followed by; (b) admixing mica to said preheated polymerin an amount from about 10 to about 50 percent weight based on thecombined weight of the resin and mica and maintaining the mixture belowabout 425° F.; followed by, (c) extruding the mixture. Polymer may bemelted exclusively through the application of shear, or the shear may besupplemented through heating by infrared radiation or ordinary heatingcoils or performed externally to the mixing chamber. Preferably, thebasic odor suppressing agent is added simultaneously with the mica.

[0020] It is desirable to keep the duration of the step of admixing micaand a basic odor suppressant agent to the mixture relatively short so asnot to generate compounds which cause odor and to preserve the particlesize and aspect ratio of the mica. Accordingly, the step of admixing themica should be no more than about five minutes with the duration of theadmixing step of less than about three minutes being even morepreferred. Any suitable means may be used to carry out the sequentialprocess in accordance with the invention, however, the process isnormally carried out in a batch mode in a mixing chamber provided with apair of rotating rotors in an apparatus referred to in the industry as aBanbury type mixer. One may choose to use a twin screw extruder or aBuss kneader to practice the inventive process if so desired, providedthat appropriate elements are used to minimize shear heating.

[0021] In a further aspect of the invention, there is provided a processfor making pottery-like, micronodular, low-odor microwaveablecontainers. The inventive process is generally directed to a process forforming a microwaveable, disposable, rigid and strong, mica and basicinorganic or organic compound filled polyolefin containers having foodcontact compatible olfactory properties, the polyolefin being selectedfrom the group consisting of polypropylene and polypropylenepolyethylene copolymer or blend, and a mixture of these wherein theinorganic or organic compound is selected from the group consisting ofcalcium carbonate, sodium carbonate, potassium carbonate, bariumcarbonate, aluminum oxide, sodium silicate, sodium borosilicate,magnesium oxide, strontium oxide, barium oxide, zeolites, sodiumphosphate, potassium phosphate, magnesium phosphate, sodium stearate,calcium stearate, potassium stearate, sodium citrate, potassium citrate,hydroxides of these elements, and mixtures of these organic compounds,mixtures of silicon dioxide with one or more of the following oxides:magnesium oxide, calcium oxide, barium oxide, and mixtures of one ormore of the basic inorganic or organic compounds set forth herein. Theprocess involves the steps of:

[0022] (a) forming an extrudable admixture of the polyolefin resin,mica, and the basic inorganic compound or basic organic compound;

[0023] (b) extruding the extrudable admixture of the polyolefin resin,mica, and the basic inorganic compound or the basic organic compound atelevated temperature;

[0024] (c) passing the resulting extruded admixture of the polyolefinresin and mica and the basic inorganic compound or the basic organiccompound through a multiple roll stack, at least one roll of said stackhaving a matte finish;

[0025] (d) thermoforming the extruded admixture of the polyolefin,resin, mica, and the basic inorganic compound or organic compound; and

[0026] (e) recovering a container having a micronodular surface andexhibiting a melting point of no less than 250° F.

[0027] The container is dimensionally stable and resistant to grease,sugar, and water at temperatures up to about 220° F. and has sufficienttoughness to be resistant to cutting by serrated flatware. The amount ofthe basic inorganic compound or basic organic compound added issufficient to reduce carbonyl moiety containing decomposition productsto provide containers with suitable food contact compatible olfactoryproperties.

[0028] The process most preferably includes:

[0029] (a) forming an extrudable admixture of the polyolefin resin,mica, and the basic inorganic compound or basic organic compound;

[0030] (b) extruding the extrudable admixture of the polyolelfin resinand mica and the basic inorganic compound or the basic organic compoundat elevated temperature;

[0031] (c) passing the resulting extruded admixture of the polyolefinresin and mica and the basic inorganic compound or the basic organiccompound through a multiple roll stack, at least one roll of the stackhaving a matte finish;

[0032] (d) passing the extruded admixture of the polyolefin resin, mica,and basic inorganic compound or the basic organic compound at leastpartially around the roll having a matte finish;

[0033] (e) controlling the speed of the extrusion process, the size,temperature and configuration of the roll stack such that the surface ofthe extruded admixture of the polyolefin resin, mica, and the basicinorganic or organic compound not in contact with the matte roll has acoarse-grained structure;

[0034] (f) thermoforming the extruded admixture of the polyolefin,resin, mica, and the basic inorganic compound or organic compound; and

[0035] (g) recovering a container having a micronodular surface and arough surface and exhibiting a melting point of no less than 250° F.

[0036] The coarse-grained structure of the surface of the extrudedadmixture of the polyolefin resin, mica, and the basic inorganiccompound or basic organic compound not in contact with said matte rollis formed by transversing the extruded admixture of the polyolefinresin, mica, and the basic inorganic compound or basic organic compoundthrough a curvilinear path and at least partially solidifying thesurface of the extruded admixture of polyolefin resin, mica, and thebasic inorganic compound or basic organic compound not contacting saidmatte roll while that surface is in tension relative to the surfacecontacting said matte roll. The container may be a plate, a cup, a bowl,a tray, a bucket, a souffle dish or the like.

[0037] Thermoforming is typically conducted at a sheet temperature offrom about 260° to about 310° F., and more preferably at a temperatureof from about 280° to about 300° F.

[0038] There is provided in a still further aspect of the invention acrack-resistant, thermoformed food contact article having a wallthickness ranging from about 10 to about 80 mils consisting essentiallyof from about 40 to about 90 G weight percent of a polypropylenepolymer, from about 10 to about 50 percent by weight mica, from about 1to about 15 percent by weight polyethylene, from about 0.1 to about 5weight percent titanium dioxide and optionally including a basic organicor inorganic compound. The basic compound is, generally speaking, thereaction product of an alkali metal or alkaline earth element withcarbonates, phosphates, carboxylic acids as well as alkali metal andalkaline earth element oxides, hydroxides, or silicates and basic metaloxides, including mixtures of silicone dioxide with one or more of thefollowing oxides: magnesium oxide, calcium oxide, barium oxide, andmixtures thereof. A particularly preferred article is where the basicorganic or inorganic compound is calcium carbonate which is present inan amount of from about 5 to about 20 weight percent.

[0039] Polyethylene is more typically present from about 2.5 to about 15weight percent, preferably from about 4 to about 5 weight percent of thecrack resistant article.

[0040] Titanium dioxide is included in various amounts, from about 0.1to about 3 percent by weight being typical; from about 0.25 to 2 percenttitanium dioxide may be included. Preferably, titanium dioxide isincluded in at least 0.5 percent by weight.

[0041] The caliper, or wall thickness, of the articles is usually fromabout 0.010 to about 0.050 inches or from about 10 mils to 50 mils. Acaliper of from about 15 to 25 mils is most typically employed.

[0042] While any suitable polypropylene polymer may be employed, themost preferred polymer is isotactic polypropylene having a melt index inthe range of from about 0.3 to 4, with a melt index of about 1.5 beingtypical. The polyethylene employed may be HDPE, LLDPE, LDPE or MDPE,mixtures thereof or a polyethylene with bimodal molecular weightdistribution. Polypropylene is sometimes referred to hereafter as “PP”.

[0043] The inventive compositions from which the crack resistantarticles are made do not include coupling agents such as maleicanhydride containing polypropylene as further described herein, but mayoptionally include other components which do not alter the basic andnovel characteristics of the crack-resistant plates. For example,nucleants such as sodium benzoate in amounts detrimental to crackresistance are to be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will become more fully understood from thedetailed description given herein below and the accompanying drawings,which are given by way of illustration only, and thus, are notlimitative of the present invention and wherein:

[0045]FIG. 1 is a schematic flow diagram of the sheet extrusion process;

[0046]FIG. 2 is a schematic flow diagram of the thermoforming processfor the manufacture of plates and containers having a micronodularsurface;

[0047]FIG. 3 is a chromatograph of a melt processed polypropylene/micacomposition exhibiting relatively high odor;

[0048]FIG. 4 is a chromatograph of a melt processed polypropylene/micacomposition exhibiting relatively low odor;

[0049]FIG. 5 is a plot of sensor responses vs. time for an automatedaroma scanning device;

[0050]FIG. 6 is a plot of the response integrals for the 32 sensors inan aroma scanning device for 3 different polypropylene/micacompositions;

[0051]FIG. 7 is a schematic diagram of a Banbury type compounder;

[0052]FIG. 8 is a plot of current draw vs. time for a compoundingprocess according to the present invention in a compounder of the typeshown in FIG. 7:

[0053]FIG. 9A is a scanning electron photomicrograph of a plate (upperpicture) and FIG. 9B is a scanning electron photomicrograph of a sheet(lower picture) of this invention wherein there is shown themicronodular food contact surface of the plate but not so for the neatextruded sheet;

[0054]FIG. 10 is a graph plotting gloss versus mica level;

[0055]FIG. 11 is a graph plotting the plate rigidity versus mica level;

[0056]FIG. 12A is a scanning electron photomicrograph of a sheet of thisinvention showing a matted surface and FIG. 12B is a scanning electronphotomicrograph of a non-matted surface;

[0057]FIGS. 13A and 13B are scanning electron photomicrographs of sheetsof this invention showing two high gloss sides;

[0058]FIGS. 14 A and B are isometric drawings of a plate of thisinvention;

[0059]FIGS. 15 A through C include cross sectional views of the plateshown in FIGS. 14 A and B;

[0060]FIG. 16 is a radial cross-section of the plate shown in FIGS. 14Aand B;

[0061]FIG. 17 is a schematic profile of the plate shown in FIGS. 14A andB, beginning from the center line of the plate, formed in accordancewith the present invention;

[0062]FIG. 18 is a drawing of another plate of this invention;

[0063]FIG. 19 is a cross sectional view of the plate shown in FIG. 18;

[0064]FIG. 20 is a schematic profile of the plate shown in FIG. 18beginning from the center line;

[0065]FIGS. 21A and 21B are drawings of a tray included in thisinvention;

[0066]FIGS. 22 A, B and C include a cross sectional view of the trayshown in FIGS. 21A and B;

[0067]FIG. 23 is a radial cross section of the tray shown in FIGS. 21Aand B;

[0068]FIG. 24 is a schematic profile of the tray shown in FIGS. 21A andB beginning from the center line;

[0069]FIGS. 25A and B are drawings of a bowl of this invention;

[0070]FIGS. 26A through C include a cross-sectional view of the bowlshown in FIGS. 25A and B;

[0071]FIG. 27 is a radial cross section of the bowl shown in FIGS. 25Aand B;

[0072]FIG. 28 is a schematic profile of the bowl shown in FIGS. 25A andB beginning from the center line;

[0073]FIG. 29 is a drawing of a take-out food container included in thisinvention;

[0074]FIGS. 30A and B are drawings of another bowl of this invention;

[0075]FIGS. 31A through 31C include a cross-sectional view of the bowlshown in FIGS. 30A and 30B;

[0076]FIG. 32 is a radial cross section of the bowl shown in FIGS. 30Aand 30B;

[0077]FIG. 33 is a profile of the bowl shown in FIGS. 30A and 30B;

[0078]FIG. 34 is a graph comparing the rigidity of the plates of thisinvention with prior art commercial products in the context of currentmaterial costs; and

[0079]FIG. 35 is a bar graph comparing the heat resistance of the platesof this invention with prior art commercial products.

DETAILED DESCRIPTION OF THE INVENTION

[0080] The aesthetically pleasing microwaveable disposable, rigid andstrong containers including plates, bowls, cups, trays, buckets, souffledishes and lids comprise isotactic polypropylene, propylene-ethylenecopolymer, or blends of isotactic polypropylene and propylene-ethylenecopolymer coupled with a mixture of a platy inorganic mineral such asmica and basic inorganic or organic compounds which are the reactionproduct of an alkali metal or alkaline earth element with carbonates,hydroxides, phosphates, carboxylic acids, mixtures of silicon dioxidewith one or more of the following oxides: magnesium oxide, calciumoxide, barium oxide, and mixtures of one or more of the basic organic orinorganic compounds set forth herein.

[0081] Suitably the basic inorganic or organic compounds are selectedfrom the group consisting of calcium carbonate, sodium carbonate,potassium carbonate, barium carbonate, aluminum oxide, sodium silicate,sodium borosilicate, magnesium oxide, strontium oxide, barium oxide,zeolites, sodium phosphate, potassium phosphate, magnesium phosphate,mixtures of silicon dioxide with one or more of the following oxides:magnesium oxide, calcium oxide, barium oxide, and mixtures of these orother basic inorganic or organic compounds such as sodium stearate,calcium stearate, potassium stearate, sodium citrate, potassium citrate,and mixtures of these basic organic compounds.

[0082] The function of the basic inorganic compound or organic compoundis to minimize the formation of odor-causing compounds in themica/polyolefin composition and thus provide products with food contactcompatible olfactory properties for consumer use. In this connection,the amount of the basic inorganic compound or organic compound added iscontrolled to be sufficient to reduce formation of decompositionproducts to sufficiently low levels to provide containers and plateswith suitable food contact compatible olfactory properties. Suitably 5to 15 weight percent of the container comprises the basic inorganiccompound, advantageously about 8 to 12 percent. When the basic organiccompounds are used, lower quantities are required, suitably from about0.5 to 2.5 weight percent, advantageously 1.0 to 1.5 percent. Couplingagents and pigments may be utilized. Maleic anhydride and acrylicmodified polypropylenes are suitable coupling agents for someembodiments.

[0083] The containers, bowls, trays and plates of this invention arepreferably produced by compounding a suitable resin/mica composition;forming it into a sheet as shown in FIG. 1 and then thermoforming thesheet as shown in FIG. 2. These examples are illustrative and are notlimitative of a preferred commercial process which involves in-lineextrusion with regrind and thermoforming with multi-cavity mold beds.

[0084] Advantageously, the sheet is formed by an extrusion processutilizing the compounded polymer/mica basic inorganic compound or basicorganic compound mixtures. The final extrusion process renders a sheetwith excellent thermal properties, cut resistance, and food contactcompatible olfactory properties. Generally, injection molding isinherently not suitable for the manufacture of self-texturizedmicronodular containers, bowls, trays and plates, since injection moldedproducts are smooth plastic like articles which do not exhibit amicronodular surface or have the feel of stoneware or pottery-like look.

[0085] The aesthetically pleasing disposable microwaveable containers,trays, bowls and plates exhibit (a) food contact compatible olfactoryproperties, and (b) a melting point of at least 250° F. In addition, thecontainer or plate is dimensionally stable and resistant to grease,sugar, and water at temperatures of up to about 220° F. and are ofsufficient toughness to be resistant to cutting by serrated polystyreneflatware. The preferred mica and basic inorganic compound or the basicorganic compound filled polypropylene plates, besides exhibiting foodcontact compatible olfactory properties, exhibit on at least one side amicronodular surface and a thickness uniformity characterized by athickness coefficient of variation (COV) of less than about fivepercent.

[0086] Mica is a common name for naturally occurring inert mineral ofthe phyllosilicate chemical family, specifically potassiumaluminosilicate whereby the aluminum ions may be partially replaced byiron and magnesium and part of the chemically bound water may besubstituted by fluorine.

[0087] Mica is easily cleaved into thin, relatively regular, flexibleyet strong sheets (leaf-like flakes) with thickness in the range of halfa micron and aspect ratio as high as 300. Mica is much softer than otherinorganic fillers (wollastonite, glass) yet only slightly harder thantalc. Mica has a slippery tactile feel and low abrasiveness relative toother common inorganic fillers.

[0088] The reinforcement effect at 40 weight percent mica is equivalentto that of 30 weight percent glass fiber. Hard inorganic fibrous fillerssuch as glass (various lengths) and wollastonite (acicular structures)have serious drawbacks such as abrasiveness and are prone to fracturedegradation during conventional melt processing. Other fibrous (organic)fillers are derived from wood and vegetable sources and are not suitablefor use in the manufacture of the containers of this invention since theorganic fillers, when used in substantial amounts, tend to degradeduring processing and they are also moisture sensitive. Preferably about20 to 35 weight percent mica are used.

[0089] In some applications it may be preferred to treat the mica and/orbasic inorganic compounds prior to using them in the inventive articles.A suitable compound for this treatment is amino-silane; sometimesreferred to as a “coupling” agent.

[0090] Suitable basic inorganic and organic compounds used in theprocess include: calcium carbonate, sodium carbonate, sodium hydroxide,potassium carbonate, barium carbonate, aluminum oxide, sodium silicate,sodium borosilicate, magnesium oxide, strontium oxide, barium oxide,zeolites, sodium phosphate, potassium phosphate, magnesium phosphate,mixtures of silicon dioxide with one or more of the following oxides:magnesium oxide, calcium oxide, barium oxide, and mixtures of these orother basic inorganic or organic compounds such as sodium stearate,calcium stearate, potassium stearate, sodium citrate, potassium citrate,and mixtures of these basic compounds.

[0091] In the case where microwaveability is desired for a plasticdisposable food contact article, the not so perfect solution has beenthe use of relatively expensive high heat modified polystyrene based orheat resistant materials (e.g., unfilled PPO and SMA engineeringresins), where PPO refers to polyphenylene oxide and SMA refers tostyrene-maleic anhydride copolymer.

[0092] The mica and basic inorganic compound or basic organic compoundfilled polpropylene containers, bowls, trays and plates of thisinvention have overcome the disadvantages of the prior art typecontainers, bowls, trays and plates and are significantly superior tothem.

[0093] Mica and the basic inorganic compound or the basic organiccompound filled polypropylene is compounded by pre-blending thepolypropylene in pellet or flake form with mica powder and the basicinorganic compound or the basic organic compound powder and otheradditives (color concentrates, pigments, antioxidants, lubricants,nucleating agents, antistatic agents, etc.). This mixture is conveyedinto the feed section addition point of a twin screw compoundingextruder, or compounded in a Banbury-type mixer to provide amelt-processed polyolefin composition. Alternatively, the components areadvantageously fed separately into the same or different points ofaddition, using combinations of volumetric and/or gravimetric (i.e.,loss in weight type) feeders as further described herein.

[0094] For white pigmentation, titanium dioxide is preferred due tocombination of brightness, and opacity, as well as stability duringprocessing and final use. Surface treatment may be optionally used tofurther enhance wetting, dispersion, compatibility with matrix resinswhereas the titanium dioxide forms may be of the rutile or anatase type.Alternate white pigments may also consist of calcined clay or blends ofcalcined clay with titanium dioxide. For black pigmentation, carbonblack is preferred due to a combination of desirable characteristicssuch as blackness, and dispersibility, the latter of which can becarefully controlled by choice of particle size and surface chemistry.Carbon black is amorphous carbon in finely divided form which is made byeither the incomplete combustion of natural gas (channel black) or byreduction of liquid hydrocarbons in refractory chambers (furnace black).

[0095] A twin screw extruder provides sufficient mixing action toeffectively cause the wetting and dispersion of the filler into thepolymer matrix. The twin screw extruder may be of the co-rotating orcounter-rotating type, where each type is equipped with different screwflight elements which are appropriate for the feed, mixing, and meltmetering zones. The discharge zone normally consists of a strand diewhere the exiting molten material strands are quenched in a circulatingwater bath followed by knife cutting into pellets. In a particularlypreferred embodiment, a Banbury-type mixer is used for compounding theresin, mica and basic compound as further described herein.

[0096] Low molecular weight additives such as waxes, fluorinatedpolymers, and other specialty lubricants are suitably used as processaids to reduce the melt viscosity and improve throughput. Polyethleneresin may also be added to the blend. Other additives may includenucleating agents and antistatic agents. Antioxidants may be added insmall amounts, generally less than one weight percent, to minimize shearand thermal degradation of the polypropylene during the extrusion andforming processes as well as to promote the chemical stability of thesheet prior to and during final article use. Suitable antioxidants areadvantageously selected from the group of phenolics and phosphites andblends thereof. These are produced by Ciba-Geigy and General ElectricCorporation.

[0097] Plastic sheet extrusion equipment is suitable for the manufactureof multilayered or single layered mica and the basic inorganic ororganic compound filled sheets of a polyolefin selected from the groupconsisting of polypropylene, polypropylene/polyethylene copolymer orblend, and mixtures of these. Melt strength of the sheets is improvedwhen mica is used as a filler since geometry of the mineral in the formof high aspect ratio flakes serves to provide “inter-particleconnectivity” or physical cross-linking. The food contact compatibleolfactory properties are enhanced when in addition to the mica, basicinorganic compounds or organic compounds such as calcium carbonate,sodium carbonate, potassium carbonate, barium carbonate, aluminum oxide,sodium silicate, sodium borosilicate, magnesium oxide, strontium oxide,barium oxide, zeolites, sodium phosphate, potassium phosphate, magnesiumphosphate, mixtures of silicon dioxide with one or more of the followingoxides: magnesium oxide, calcium oxide, barium oxide, and mixtures ofthese or other basic inorganic or organic compounds such as sodiumstearate, calcium stearate, potassium stearate, sodium citrate,potassium citrate, and mixtures of these are mixed with mica and thepolyolefin to produce the containers of this invention.

[0098] In FIG. 1 a process is shown for the manufacture of a singlelayer mica filled polypropylene sheet or polypropylene filled with micaand basic inorganic compounds or organic compounds set forthhereinabove. Previously compounded and pelletized mixtures ofpolypropylene, mica and the basic inorganic compound or organiccompound, and other additives are gravity fed by a hopper 10 into thefeed zone of a single screw extruder system. Primary extruder 11 has a 2inch diameter screw with a 24/1 length to diameter ratio. Optionallymultilayer coextruded sheet can be produced by utilizing at least oneadditional single screw extruder 12, 13, 14 in conjunction with acombining feedblock with proper melt piping and manifold arrangements.Suitably one to seven screw extruders are employed, preferably three. Aflexible lip flat sheet die 15 having a width of 31 inches was used.

[0099] The sheet of this invention 16 enters the sheet takeoff portion(i.e., after the molten material exits the die) compromising athree-roll polishing/casting unit 17 with individually temperaturecontrolled rolls, a two-rubber roll sheet pull unit 18, and a dualturret, dual shaft winder, whereby only one shaft winder roll 19 may beused. The three takeoff units were mechanically tied together, were on acommon track, and can be automatically traversed from close die lipproximity to about 36 inch distant. During the extrusion process, thedistance between the die exit and the casting unit was maintained at 2inches. These three chrome rolls comprising the sheet casting unit areindividually temperature controlled by integral oil circulating pumpsand heat exchangers. Nip gaps are adjustable. A speed differentialbetween cast rolls and pull rolls is normally maintained such that pullroll speed is approximately within ten percent (10%) of cast roll speed.On a pilot line, achievable line speeds are in the range of 1-12.5 feetper minute; while for a sheet on the order of 20 mil thick, the linespeed is about 5-6 feet per minute. The sheet is wound on a roll 19.Table 1 shows the sheet process conditions employed for the sheetextrusion of mica and basic inorganic compound or the basic organiccompound filled polypropylene and the unfilled polypropylene control. Ina commercial operation, the speed is increased by a factor of 10 to 20times.

[0100] Thermoforming is the pressing or squeezing of pliable materialinto final shape. In the simplest form, thermoforming is the draping ofa softened sheet over a shaped mold. In the more advanced form,thermoforming is the automatic, high speed positioning of a sheet havingan accurately controlled temperature into a pneumatically actuatedforming station whereby the article's shape is defined by the mold,followed by trimming and regrind collection.

[0101] Forming techniques other than conventional thermoforming are alsosuitable for the manufacture of articles described in the presentinvention. These include variations such as presoftening the extrudedsheet to temperatures below the final melting temperature, cutting flatregions (i.e., blanks) from the sheet, transfer of blanks by gravity ormechanical means into matched molds whereby the blanks are shaped intothe article by heat and pressure. The sheet from which the blanks havebeen cut out is collected as regrind and is recyclable. Conventionalpaperboard pressing equipment and corresponding forming tooling isoptionally modified to produce articles of this invention.

[0102] The extruded sheet used in a preferred thermoforming process asshown in FIG. 2 has a thickness of about 0.010 to 0.080 inches (10 to 80mils), suitably 0.010 to 0.050 inches. For the plates the preferredthickness is about 0.015 to 0.025 inches. Suitable mica filler loadinglevel in the extruded sheet is in the range of 10 to 50 weight percent,more preferably 20-50 weight percent and most preferably 20-35 weightpercent. To achieve suitable food contact compatible olfactoryproperties, the basic inorganic compound loading level should be 5 to 15weight percent, advantageously 8 to 12 weight percent. For the basicorganic compound the loading levels should be 0.5 to 2.5 weight percent,preferably 1.0 to 1.5 weight percent. The mica flake aspect ratio is inthe range of 30-300, more preferably 15-250, with particle size range ofabout 10-500 microns. The extruded sheet comprises isotacticpolypropylene homopolymer or polypropylene polyethylene copolymer orblend or a mixture of these as base resin, preferably having a melt flowindex in the range from about 0.3 to about 4.0, more preferably 0.5 -2.0 and most preferably about 1.5. Propylene copolymers or blends withethylene levels in the range of 1-10 mole percent, more preferably 2-5mole percent, are optionally used.

[0103] The preferred type of mica is muscovite, which is the most commonform in commerce. Optionally other less common mica types such asphlogopite, biotite and fluorphlogopite are used. Although there are aninfinite number of compositions possible for these four generic typesdue to isomorphous substitution which are mine specific, the selectionof particular grades is driven by particle aspect ratio, particle size,price and availability.

[0104] Suitably the extruded sheet includes coloring agents foraesthetic appeal, preferably titanium dioxide, carbon black, and otheropacifying agents in the range of 0.5-8 weight percent based on totalcomposition, preferably 1.5 to 6.5 weight percent. The extruded sheetcomprises minor amounts of other additives such as lubricants andantioxidants. These articles of manufacture may be suitably colored withpigments or dyes. Pigments are defined as small insoluble organic orinorganic particles dispersed in the resin medium to promote opacity ortranslucency. Usual pigments include carbon black, titanium dioxide,zinc oxide, iron oxides, and mixed metal oxides. Dyes are organic andsoluble in the plastic, and may be used alone or in combination withpigments to brighten up pigment based colors. All such colorants may beused in a variety of modes which include dry color, conventional colorconcentrates, liquid color and precolored resin.

[0105] Mica and the basic inorganic compound or the basic organiccompound filled polypropylene sheets are suitably formed into plates,bowls, cups, trays, buckets, souffle dishes, and containers using aforming or thermoforming process disclosed herein. In a pilot process,these articles of manufacture and containers may be made using the CometStarlett thermoformer unit. This machine is capable of vacuum formingproducts from heat softened thermoplastic materials and is schematicallydepicted in FIG. 2. Sheet portions 23 having dimensions of 17.5 inchesby 16.25 inches were clamped on two opposing sides and inserted into anoven indicated at 22 equipped with upper 20 and lower 21 heaters,whereby heater input settings were in the range of 20-30 percent andhold times were on the order of 60-80 seconds. Under these conditions,the oven air temperature as recorded by a digital thermocouple was inthe range of 221° F. to 225° F., while the sheet surface temperature, asrecorded by adhering indicator thermocouples, was approximately 330° F.to 340° F.

[0106] When the clamped and heat softened sheet 23 exits the oven 22, itmay be vacuum formed by either procedure (A) or (B) in a commercialprocess. Both methods utilize only one mold which is suitably fabricatedfrom epoxy thermoset materials or suitable mold materials includingaluminum, steel, beryllium, copper and the like. Mode (A) uses a malemold 24 whereby the sheet is sucked up to conform to it by means ofvacuum where the vacuum ports are present on the mold base as well as onthe periphery side of the container (i.e., flange area). Mode (B)arrangement is such that the vacuum direction is opposite to mode (A),where again vacuum holes are located around the base and periphery. Inthe case of mode (B), a female mold 25 is used, and this arrangement ispreferred since the air side of the sheet corresponds to the foodcontact side. In mode (B) the food contact side undergoes a beneficialtexturizing effect as a result of the heat treatment, whereby the resinflows around and outward from the mica particles close to the surfacecausing the mineral to become more exposed which creates a micronodularsurface as manifested by decreased gloss and increased surfaceroughness. The micronodular surface gives the container a stoneware orpottery-like appearance.

[0107] Suitably a process for forming a disposable, microwaveable, rigidand strong mica and the basic inorganic compound or the basic organiccompound filled polyolefin container, plate, bucket, or the like, havingfood contact compatible, olfactory properties wherein the polyolefin isselected from polypropylene, polypropylene polyethylene copolymer orblend and the basic inorganic compound and the basic organic compound isselected from the group consisting of calcium carbonate, sodiumcarbonate, potassium carbonate, barium carbonate, aluminum oxide, sodiumsilicate, sodium borosilicate, magnesium oxide, strontium oxide, bariumoxide, zeolites, sodium phosphate, potassium phosphate, magnesiumphosphate, mixtures of silicon dioxide with one or more of the followingoxides: magnesium oxide, calcium oxide, barium oxide, and mixtures ofthese or other basic inorganic or organic compounds such as sodiumstearate, calcium stearate, potassium stearate, sodium citrate,potassium citrate and mixtures of these comprise the steps of:

[0108] (a) forming an extrudable admixture of the polyolefin resin,mica, and the basic inorganic compound or the basic organic compound;

[0109] (b) extruding said extrudable admixture of the polyolefin resin,mica and the basic inorganic compound or the basic organic compound atelevated temperature;

[0110] (c) passing the resulting extruded admixture of the polyolefinresin, mica and the basic inorganic compound or the basic organiccompound through a multiple roll stack, at least one roll of said stackhaving a matte finish;

[0111] (d) passing said extruded admixture of the polyolefin resin andmica and the basic inorganic compound or the basic organic compound atleast partially around said roll having a matte finish;

[0112] (e) controlling the speed of said extrusion process, the size,temperature and configuration of said roll stack such that the surfaceof said extruded admixture of polyolefin resin, mica and the basicinorganic compound or the basic organic compound not in contact withsaid matte roll has a coarse-grained structure; and

[0113] (f) thermoforming said extruded admixture of polyolefin, mica andthe basic inorganic compound or the basic organic compound andrecovering a container, plate, bucket, or the like, having amicronodular surface and a rough surface, exhibiting a melting point ofno less than about 250° F.; the container, plate, bucket, etc., beingdimensionally stable and resistant to grease, sugar and water attemperatures up to about 220° F. and having sufficient toughness to beresistant to cutting by serrated flatware and exhibiting food contactcompatible olfactory properties.

[0114] Advantageously, the coarse-grained structure of the surface ofsaid extruded admixture of polyolefin resin, mica and the basicinorganic compound or the basic organic compound not in contact withsaid matte roll is formed by transversing the extruded admixture of thepolyolefin resin, mica and the basic inorganic compound or the basicorganic compound through a curvilinear path and at least partiallysolidifying the surface of said extruded admixture of polyolefin resin,mica and the basic inorganic compound or the basic organic compound notcontacting said matte roll while that surface is in tension relative tothe surface contacting the matte roll.

[0115] Generally, a process for forming a mica basic inorganic compoundor basic organic compound filled polypropylene container, plate, bucket,tray, bowl, or the like, comprises the steps of:

[0116] (a) forming an extrudable admixture of the polypropylene resin,mica and the basic inorganic compound or the basic organic compound;

[0117] (b) extruding said extrudable admixture of the polypropyleneresin, mica and the basic inorganic compound or the basic organiccompound at elevated temperature;

[0118] (c) passing the resulting extruded admixture of the polypropyleneresin, mica and the basic inorganic or the basic organic compoundthrough a multiple roll stack, at least one roll of said roll stackhaving a matte finish;

[0119] (d) passing said extruded admixture of the polypropylene resin,mica and the basic inorganic compound or the basic organic compound atleast partially around said roll having a matte finish;

[0120] (e) controlling the speed of said extrusion process, the size,temperature and configuration of said roll stack such that the surfaceof said extruded admixture of the polypropylene resin, mica and thebasic inorganic compound or the basic organic compound in contact withsaid matte roll has a matted structure; and

[0121] (f) thermoforming said extruded admixture of polypropylene resin,the mica and the basic inorganic compound or the basic organic compound,and recovering a container, plate, bucket, or the like having amicronodular surface and exhibiting a melting point of no less that 250°F., the container, plate, bucket, or the like being dimensionally stableand resistant to grease, sugar and water at temperatures up to about220° F. and having sufficient toughness to be resistant to cutting byserrated flatware and further exhibiting food contact compatibleolfactory properties.

[0122] A process for forming a mica and the basic inorganic compound orthe basic organic compound filled polypropylene sheet suitable forthermoforming micronodular containers and plates comprises the steps of:

[0123] (a) forming an extrudable admixture of the polypropylene resin,mica and the basic inorganic compound or the basic organic compound;

[0124] (b) extruding said extrudable admixture of the polypropyleneresin, mica and the basic inorganic compound or the basic organiccompound at elevated temperature;

[0125] (c) passing the resulting extruded admixture of the polypropyleneresin, mica and the basic inorganic compound or the basic organiccompound through a multiple roll stack, at least one roll of said rollstack having a matte finish;

[0126] (d) passing said extruded admixture of the polypropylene resin,mica and the basic inorganic compound or the basic organic compound atleast partially around said roll having a matte finish;

[0127] (e) controlling the speed of said extrusion process, the size,temperature and configuration of said roll stack such that the surfaceof said extruded admixture of the polypropylene resin, mica and thebasic inorganic compound or the basic organic compound not in contactwith said matte roll has a coarse structure; and

[0128] (f) the surface in contact with the matte roll has a mattesurface; and

[0129] (g) recovering a sheet having a matted surface and a coarsesurface, said sheet comprising polypropylene, mica and the basicinorganic compound or the basic organic compound moieties. The sheet hasfood contact compatible olfactory properties.

[0130] Advantageously, other thermoforming arrangements are suitable andmay be preferred in conventional sheet and web feed thermoformingcommercial production operations. Alternative arrangements include theuse of drape, vacuum, pressure, free blowing, matched die, billow drape,vacuum snap-back, billow vacuum, plug assist vacuum, plug assistpressure, pressure reverse draw with plug assist vacuum, reverse drawwith plug assist, pressure bubble immersion, trapped sheet, slip,diaphragm, twin-sheet cut sheet, twin-sheet rollfed forming or anysuitable combinations of the above. Details are provided in J. L.Throne's book, Thermoforming, published in 1987 by Coulthard. Pages 21through 29 of that book are incorporated herein by reference. Suitablealternate arrangements also include a pillow forming technique whichcreates a positive air pressure between two heat softened sheets toinflate them against a clamped male/female mold system to produce ahollow product. Metal molds are etched with patterns ranging from fineto coarse in order to simulate a natural or grain like texturized look.Suitably formed articles are trimmed in line with a cutting die andregrind is optionally reused since the material is thermoplastic innature. Other arrangements for productivity enhancements include thesimultaneous forming of multiple articles with multiple dies in order tomaximize throughput and minimize scrap.

[0131] Various measurements used herein include melt flow index, SSIrigidity (sometimes referred to below as simply “rigidity”), ParkerRoughness and so forth. Unless otherwise indicated explicitly or bycontext, these terms have the meaning set forth below.

[0132] The melt flow rate (MFR) or melt index is a common and simplemethod for determining the flow properties of molten polymers. (As usedherein, ASTM D 1238-95, Condition 230/2.16). Resin is introduced andmelted in a cylindrical space. After temperature equilibration isreached, a weight is used to push a plunger vertically downward wherebythe resin is extruded through a narrow orifice. The usual testtemperature and the temperature utilized herein for polypropylene is230° C. and the load is 2.16 Kg. Extruded material is collected andweighed and the time required to extrude a specific weight is recorded.MFR or melt index is expressed as grams per minutes, or grams per 10minutes, which is the weight of material extruded in a 10 minute timeperiod. MFR is inversely proportional to both polymer viscosity andpolymer molecular weight.

[0133] SSI rigidity is measured with the Single Service Institute PlateRigidity Tester originally available through Single Service Institute,1025 Connecticut Ave., NW. Washington, D.C. The SSI Rigidity testapparatus has been manufactured and sold through Sherwood Tool, Inc.,Kensington, Conn. This test is designed to measure the rigidity (i.e.resistance to buckling and bending) of paper and plastic plates, bowls,dishes, and trays by measuring the force required to deflect the rim ofthese products a distance of 0.5 inch while the product is supported atits geometric center. Specifically, the plate specimen is restrained byan adjustable bar on one side and is center fulcrum supported. The rimor flange side opposite to the restrained side is subjected to 0.5 inchdeflection by means of a motorized cam assembly equipped with a loadcell, and the force (grams) is recorded. SSI rigidity is expressed asgrams per 0.5 inch deflection. A higher SSI value is desirable sincethis indicates a more rigid product. All measurements were done at roomtemperature and geometric mean averages for the machine and crossmachine direction are reported.

[0134] The Parker Roughness method was used to determine roughness usingthe Messmer Parker Print-Surf Roughness. Operation procedure details arereferenced in the Messmer Instruments Ltd. User manual for theinstrument (Model No. ME-90) which is distributed by Huygen Corporation.The flat specimen is clamped under 1 Mpa pressure against a narrowannular surface by a soft backing and the resistance of air flow of thegap between the specimen and the annulus is measured. The air flow isproportional to the cube of the gap width and the roughness is expressedas the root mean cube gap in units of micrometers. Higher Parkerroughness values indicate higher degrees of surface roughness.

[0135] Gloss is reported as “gloss units at 75 or 60 degrees.” Glossmeasurements were conducted following TAPPI Standard Method T-480-OM 92.

[0136] The following examples are illustrative of the present invention.It should be understood that the examples are not intended to limit theinvention and that various modifications may be made by those skilled inthe art without changing the essential characteristics of the invention.

EXAMPLES 1- 8

[0137] Mica filled polypropylene sheets (20 mil) and unfilledpolypropylene sheets (22 mil) were extruded, as shown and described inconnection with in FIG. 1, with conditions specified in Table 1. Theseextrusion process conditions may be varied as necessary to producesheets which are of acceptable quality. Specifically, the operabletemperature ranges for barrel zones 1,2, and 3 are about respectively,350 to 425° F., and 450 to 500° F. the adaptor, feedblock, and dietemperatures can all be in about the range of 450 to 500° F. the rangeof values for extruder drive amperes, extruder speed, melt pressure, diepressure, chill roll temperature, and line speed are about respectively,12 to 20 amp., 60 to 100 RPM, 1500 to 2500 psi, 450 to 650 psi, 120 to140° F., and 3 to 8 FPM. Sheets are subsequently vacuum thermoformedinto plates and other containers and lids as set forth in FIGS. 14through 33. There is reported in Tables 2 and 3, respectively, rigidityvalues and caliper data for the sidewall, bottom, and flange (rim) areasof vacuum formed plates using condition (B) of FIG. 2 and having adiameter of 10.25 inches. In each table, individual rigidity values areshown for each specimen. In addition, the caliper uniformity forsidewall, bottom, and flange areas are reported for each specimen, alongwith the summary statistics. Specifically, the caliper of each platespecimen in Tables 2 and 3 was measured ten times using a Fowler gaugefor each of the three regions of interest consisting of the sidewall,bottom, and flange areas, and the average value for each plate specimenis reported along with the corresponding standard deviation in thousandsof inches or mils (i.e., individual plate statistics). In the case ofthe three plates of Table 2, the caliper summary statistics (expressedin the average properties row) were obtained on the basis of averaging30 measurements, wherein the standard deviation is reported for each ofthe three regions of interest. In the case of the five plates of Table3, the caliper summary statistics were calculated on the basis ofaveraging 50 measurements where again the standard deviation is reportedfor each of the three regions of interest. Therefore, the caliper dataof Tables 2 and 3 located in the average property rows pertain to globalstatistics rather than individual plate statistics. The caliperuniformity parameter consists of the coefficient of variation (COV)which is calculated as the standard deviation of caliper divided by themean caliper, whereas the ratio is multiplied by 100, whereas the abovedescribed global averages and associated standard deviations areemployed. A lower COV value is desirable since it signifies improvedcaliper uniformity for mica filled polypropylene plates with respect tounfilled polypropylene plates. Tables 2 and 3 show that mica reduces COVof polypropylene from 9.9 to 4.3 in sidewall and from 9.6 to 2.0 in theflange area. Therefore, caliper uniformity in sidewall improved by morethan a factor of 2 and caliper uniformity in the flange improved by overa factor of 4. The improvement of caliper uniformity is critical forpromoting plate dimensional stability during food transport andmicrowave cooking operations. In great contrast to mica filledpolypropylene plates, the unfilled polypropylene plates exhibited poorquality as evidenced by poorly defined rim area, and sharkskin, veryrough surface. These data demonstrate that mica greatly improves thedrawability of polypropylene as evidenced by improved caliperuniformity, as well as improved thermoformability, both of which are dueto enhanced melt strength relative to unfilled polypropylene. Mica isthe preferred reinforcing mineral filler for enhancing the melt strengthbecause of its highly regular, high aspect ratio morphology which can bethought of as resulting in “inter-particle connectivity” or “physicalcross-linking”. The significant reinforcing effect of mica is alsoevidenced by a SSI plate rigidity value of 671 grams per 0.5 inches forPP/mica at a basis weight of about 350 lbs. per square foot ream versus342 grams per 0.5 inches for unfilled PP at a basis weight of about 280lbs. per 3000 square foot ream. TABLE 1 Sheet Extrusion Conditions forMica Filled Polypropylene and Unfilled Polypropylene CONDITION PP/MICAUNFILLED PP Barrel Zone 1 (° F.) 395 395 Barrel Zone 2 (° F.) 425 425Barrel Zone 3 (° F.) 475 475 Adaptor (° F.) 470 450 Feed block (° F.)470 460 Die Zones 1-3 (° F.) 470 475 Extruder RPM 80 70 Drive amperes 1619 Melt pressure (psi) 1700 1780 Die pressure (psi) 550 825 Line speed(FPM) 6.1 5.0 Chill roll temp. (° F.) 130 137

[0138] TABLE 2 Caliper and Rigidity Data for 10-1/4 Inch PlatesThermoformed From Unfilled Polypropylene Sheet Plate Specimen RigiditySidewall Bottom Caliper Flange Example (g/0.5 in.) Caliper (mil) (mil)Caliper (mil) 1 364 18.7 ± 1.9 20.7 ± 0.8 22.9 ± 2.8 COV* 10.1 3.9 12.22 382 19.2 ± 20. 20.6 ± 0.4 23.3 ± 0.8 COV 10.4 1.9 3.4 3 280 19.6 ± 1.920.6 ± 0.5 23.3 ± 2.8 COV  9.7 2.4 12.0 Average 342 ± 54.4 19.19 ± 1.8920.64 ± 0.58 23.15 ± 2.21 Properties COV  9.85 2.81 9.55

[0139] TABLE 3 Caliper and Rigidity Data for 10-1/4 inch PlatesThermoformed From Polypropylene/Mica/TiO₂ Sheet Plate Bottom FlangeSpecimen Rigidity Sidewall Caliper Caliper Example (g/0.5 in.) Caliper(mil) (mil) (mil) 4 705 18.3 ± 1.1 17.4 ± .05 18.2 ± 1.0 COV* 6.0 2.95.5 5 659 17.0 ± 1.5 17.9 ± 0.7 18.4 ± 0.5 COV 8.8 3.9 2.7 6 654 17.3 ±1.6 17.0 ± 0.6 18.2 ± 0.7 COV 9.2 3.5 3.8 7 669 16.9 ± 1.2 16.7 ± 1.118.9 ± 0.8 COV 7.1 6.6 4.2 8 668 16.3 ± 1.0 16.3 ± 0.9 19.0 ± 0.9 COV6.1 5.5 4.7 Average 671 ± 20  17.3 ± 0.76 17.1 ± 0.6  18.5 ± 0.38Properties COV 4.3 3.5 2.0

EXAMPLES 9-11

[0140] Thirty percent-mica-and ten percent calcium carbonate filledpolypropylene sheet was run on a commercial extrusion line. The extruderwas a 6″ Egan single screw with an EDI flex lip die. In these Examples9 - 11, the resulting melt temperature was approximately 400° F. and thetemperature for Barrel Zones 1-5 were approximately 400/396, 390/390,370/370, 370/370, and 370/371 as shown in Table 4.

[0141] Lower melt temperatures are typically preferred. Process melttemperatures of 370° F. or so will help control undesirable odors in theproduct. Process melt temperature as used throughout refers to ameasured value of the temperature of a composition when thepolypropylene is molten and unless otherwise stated, is indicative ofthe maximum temperature of a particular step.

[0142] For the runs reported in Table 4, an auger feeder was installedjust above the feed throat of the extruder to introduce colorconcentrates for producing green, blue, and eggshell colored sheet. Theconcentrate was added at levels between 1% -5%. TABLE 4 ExtrusionConditions for 30% Mica/10% Calcium Carbonate Filled PolypropyleneSet/Actual Conditions Green Blue Eggshell Barrel Zone 1 Temp (F) 400/396400/398 400/399 Barrel Zone 2 Temp (F) 390/390 390/390 390/391 BarrelZone 3 Temp (F) 370/370 370/370 370/370 Barrel Zone 4 Temp (F) 370/370370/370 370/370 Barrel Zone 5 Temp (F) 370/371 370/370 370/370 AdaptorTemp (F) 370 370 370 Melt Temp (F) 400 400-405 404/405 Die Zone 1 Temp(F) 380 385 385 Die Zone 2 Temp (F) 370 370 370 Die Zone 3 Temp (F) 370370 370 Die Zone 4 Temp (F) 370 370 370 Die Zone 5 Temp (F) 380 385 385Screw RPM 30 30 30 Drive Amperes 325-345 335-352 347-350 Screen Pack 20mesh 20 mesh 20 mesh Back Pressure (psi) 2350-2510 2370-2600 2515-2680Line Speed (fpm) 30/28/20 30/28/22 27/26/20 Throughput (lb./hr.) 725 725725 Top Stack Roll Temp 120-130 120-130 120-130 (F) Middle Stack RollTemp 120-130 120-130 120-130 (F) Bottom Stack Roll 120-130 120-130120-130 Temp (F) RollGap - top (mil) 17 17 17 Roll Gap - bottom (mil) 2323 23 Nip Roll Pressure 50 80 80 Die Gap (mil) 15 middle - 30 15middle - 30 15 middle - 30 edges edges edges Die - Full Width (in) 52 5252 Die to Nip Distance (in) Approximately 4.5 Approximately 4.5Approximately 4.5 Sheet Width (in) 51.5 51.5 51.5 Sheet Caliper (mil)17.5/18.5/24 17.5/18.5/24 17.5/18/24 Color Auger Setting (%) 4 4 1 TrimRegrind Used Yes Yes No Footage Produced 12000 11000 15000

EXAMPLES 12-17

[0143] Aroma Profile Test Method

[0144] The Sensory Analysis Center at Kansas State University hasdeveloped a profiling protocol in which a highly trained panelidentifies specific odors and rates their intensity. The intensity scaleis a 15-point “universal” scale of the type typically chosen for sensorystudies, where 1 is barely perceptible or threshold and 15 is extremelystrong. If an attribute or odor component is not listed in the tableswhich follow, it means it is not present and would score a 0. The panelmembers are selected on the basis of a series of screening tests thatinclude basic taste, odor recognition, taste intensity recognition,taste intensity ranking, and a personal interview to evaluateavailability and personality traits. Training, which includes thefundamental sensory principles and all aspects of the profile technique,is done over a 4-12 month period.

[0145] The panelists work as a group to arrive at a description of theproduct. Individual results are compiled by the panel leader anddiscussion follows in which disagreements are discussed until aconsensus is reached on each component of the profile. Referencematerials and more than one session usually are required in order toreach the consensus.

[0146] The procedure for resin is to place 40 ml. of resin in a 340 ml.glass brandy snifter, which is covered with a watch glass. Sheet samplesare cut into two 2∴×2″ sections and placed in the same size brandysnifter. In testing, panelists found that some samples had initial odorcomponents that disappeared rapidly. Therefore an initial impact and asustained impact were evaluated for each sample. The initial impact wasjudged immediately after the watch glass had been removed; the sustainedimpact was judged 10 seconds after the watch glass had been removed.Typical results are shown in the Table 5 below for Low Odor and HighOdor Compositions. “Low” odor formulations were produced using lowermelt processing temperatures in compounding and adding 10% calciumcarbonate to the formulation. The sheets were prepared as shown anddescribed in connection with Examples 1 through 11. TABLE 5 High Odorvs. Low Odor Polypropylene Composites: Effect of Adding 10% CaCO₃ ODORPROFILE FOR COMPOUNDED RESIN Consensus Odor Profile on Resin ResinImpact (Kansas State University Sensory Analysis Center) Resin InitialSustained Petroleum Pungent Musty Scorched Medicinal Sweet Waxy SoapyHigh 9.0 3.5 8.0 4.0 7.0 3.5 3.0 Odor Low Odor 5.5 2.5 2.5 4.5 1.5 2.04.5 High Odor Resin Low Odor Resin 65.63% Polypropylene 55.63%Polypropylene 30% Mica 30% Mica 2.5% Coupling Agent 10% CaCO₃ 1.87%Pigment 2.5% Coupling Agent 1.87% Pigment

[0147] High Odor and Low Odor compositions were compounded utilizing theprocess melt temperatures indicated in the first column of Table 6 andformed into sheets as described above. Both resin and sheet wereevaluated for aroma profile. TABLE 6 ODOR PROFILE FOR SHEET FORMED FROMCOMPOUNDED RESIN AT TWO TEMPERATURES Sheet Impact Consensus Odor Profileon Sheet Resin Initial Sustained Petroleum Pungent Musty ScorchedMedicinal Sweet Waxy Soapy High Odor 12.0 6.0 10.0 8.0 7.5 4.5 4.0 370°F. High Odor 11.0 8.0 7.5 7.5 6.0 3.5 2.0 459° F. Low Odor 5.5 2.0 3.54.0 2.0 2.5 25 371° F. Low Odor 5.5 2.0 3.0 3.5 2.0 35 460° F.

[0148] The foregoing data demonstrates that: when a basic moietycontaining compound was added to the mica polyolefin composition, aresin was produced having suitable food contact compatible olfactoryproperties. Significant decreases in the initial and sustained odorswere observed and the scorched, pungent, and petroleum aroma componentswere removed or greatly reduced and these undesirable components seem tobe replaced with sweet, waxy, and soapy aroma components.

[0149] When compounded pellets are subjected to sheet extrusion, thosewithout calcium carbonate increase in the disagreeable components(pungent and petroleum) and increase in the initial and sustained odoroutput with subsequent processing. In contrast, when pellets containcalcium carbonate, no increase in undesirable aroma components wasobserved and no increase in the initial or sustained odor was producedwith subsequent processing. Test panel data correlated well withanalytical techniques as can be seen from the discussion and is exampleswhich follow.

[0150] C8/C9 Ketones

[0151] The precise nature of the odor causing compounds inpolypropylene/mica compositions is not known; however, it has been foundthat undesirable odors correlate well with eight carbon (C8) and ninecarbon (C9) alkyl ketones as described hereinafter, and may beassociated with such compounds.

[0152] A Likens-Nickerson steam/methylene chloride extraction techniquewas used to extract possible odor causing compounds frompolypropylene/mica compositions and produce a concentrate. Theextraction was performed until complete. The concentrate was analyzedthrough gas chromatography/mass spectrometry to produce chromatogramssuch as those shown in FIGS. 3 and 4. The abscissa is an arbitrary timescale, while the ordinate is an arbitrary abundance scale. The peak foralkyl C8 (labeled as A) ketone assigned to be 4-methyl-2-heptanone,appears on both FIGS. 3 and 4 at slightly above 16.8 on the time scaleas indicated; while the peak for C9 alkyl ketone (labeled as B),assigned to be 4,6-dimethyl-2-heptanone appears slightly below 17.6 onthe time scale in both chromatograms. Other peaks of interest on FIGS. 3and 4 are C7 ketones at slightly above 15.1, 15.6 and 16.3 on theabscissa. The peaks are respectively assigned to be 2-heptanone,3-heptanone and 4-heptanone. They are respectively labeled as C, D andE. There is also shown on both FIGS. 3 and 4 peaks for what are to beassigned to be various C7 alcohols at about 18, 18.2 and 18.8 on theabscissa. These compounds are respectively labeled as F, G and H on thediagrams and are assigned to be 2-heptanol, 3-heptanol, and 4-heptanol.The C8/C7 ratios referred to hereinafter are ratios of the abundance atthe peaks assigned to be 4-methyl-2-heptanone to the abundance at thepeak assigned to be 4-heptanone as measured by Likens-Nickersonextraction followed by gas chromtography/mass spectrometry. That is, theC8/C7 ratio for a given sample is the ratio of peak intensity (height)of peak A to the peak intensity of peak E. Similarly, the C9/C7 ratio isthe ratio of the peak intensity of peak B to the peak intensity of peakE in FIGS. 3 and 4 for a given sample.

[0153]FIG. 3 is a chromatogram characteristic of extruded pellets havinga relatively strong odor wherein the C8 and C9 ketones indicated eachhave an extractable concentration of about 10 parts per million parts byweight in the product. FIG. 4 is a chromatogram characteristic ofrelatively “low odor” extruded pellets substantially free of C8 and C9ketones as shown. Generally, “low odor” compositions reduceconcentration of C8 and C9 ketones over “high odor” compositions by ⅔with ⅕ being typical and {fraction (1/10)} being preferred. Thus, ingeneral, melt compounded compositions in accordance with the inventionhave extractable concentrations of C8 and C9 alkyl ketones of less thanabout 3.5 ppm (weight) with less than 2 ppm being typical and less than1 ppm being particularly preferred.

[0154] It can also be seen from the chromatograms in FIGS. 3 and 4 thatthe adjacent C7 ketone levels are comparable in both the “low odor” and“high odor” compositions. Thus, the C8/C7 ratio can be used as analternative indicator of desirable olfactory characteristics. Typically,“low odor” compositions in accordance with the invention have a C8/C7ratio at least five times less than high odor compositions with at leastten times less being typical.

[0155] In preferred compositions according to the invention, C8/C7ratios as measured by Likens-Nickerson extraction followed by gaschomatography/mass spectrometry are generally less than about 0.5 or soas is seen from in the examples which follow. C8/C7 ratios of less thanabout 0.3 are typical and C8/C7 ratios of less than about 0.1 areparticularly preferred. The articles of the invention and the pelletsfrom which they are made are further characterized by a relative aromaintensity index which is determined by commercially available equipmentin accordance with the procedure detailed below.

[0156] Relative Aroma Intensity Index

[0157] Melt processed compositions produced in accordance with thepresent invention, particularly extruded pellets from which articlessuch as plates and bowls are made, characteristically exhibit relativelylow odor as opposed to conventionally formulated mica/polypropylenecompositions. Generally the relative aroma intensity index (as definedherein) is less than about 1.6, with less than or equal to about 1 beingpreferred. In general, the lower the relative aroma intensity index, thelower the odor intensity of the mica/polypropylene pellets. Less than orequal to about 0.7 is most preferred with a practical lower limitbelieved to be somewhere around 0.1 or so. Thus, in accordance with theinvention, melt compositions will generally have a relative aromaintensity index of less than about 1.6 and typically from about 1.5 toabout 0.1. Within the range of from about 1.0 to about 0.1 is moretypical, while a relative aroma intensity index of from about 0.7 toabout 0.1 is preferred.

[0158] The relative aroma intensity index (RAII) of a particularmelt-processed composition is readily determined using conventionalmaterials and equipment.

[0159] The relative aroma intensity index is defined as the arithmeticaverage of all sensor integrals for a given sample divided by thearithmetic average of all sensor integrals for a standard samplespecified below; or in equation form:

[0160] RAII=Arithmetic Average of Odor Intensity over all sensors ofsample/ Arithmetic Average of Odor Intensity over all sensors ofstandard composition

[0161] A commercially available aroma scanning device is used.Typically, such devices utilize a plurality of conductivity sensors todetermine the odor of a sample. The particular device used in thediscussion which follows uses 32 sensors whose response is integratedover time. The various integrals are arithmetically averaged for eachsample (or standard composition as the case may be). This arithmeticaverage is then used in both the numerator or the denominator in theabove noted equation.

[0162] The standard composition utilized for determining RAII herein isproduced from the following components: TABLE 7 Standard CompositionAmount (Wt. Component Manufacturer Product Number Percent PolypropyleneExxon Escorene 4772 55.63 Mica Franklin L-140 30.0 Industrial Minerals,Inc. Calcium Huber Q-325 10.0 Carbonate Coupling Agent Aristech UniteNP-620 2.5 Titanium Tioxide TR-23 1.87 Dioxide

[0163] The above components were extruded on a 90 mm BerstorffCo-Rotating Twin Screw Extruder with underwater pelletizing under thefollowing conditions:

[0164] 200 rpm screw speed

[0165] with the following set temperature profile:

[0166] Zone 1 - 510° F.

[0167] Zone 2 -485° F.

[0168] Zone 3- 400° F.

[0169] Zone 4-380° F.

[0170] Zone 5 -380° F.

[0171] Zone 6-380° F.

[0172] Head Flange -425° F.

[0173] Screen Changer-425° F.

[0174] Die44° F.

[0175] Throughput appx. 900 LB/HR to produce the standard pellets. Bythe foregoing definition, these standard pellets have a relative aromaintensity index (RAII) of 1.0.

[0176] The preferred instrument to perform the aroma intensitymeasurements is an Aroma Scan® model A32 (AromaScan, Hollis, N.H., USA).This instrument employs a dynamic head space type of measurement, inwhich nitrogen gas flows through a sample vial and carries aromavolatiles to the sensors. All pellet samples are analyzed in triplicatewith the final results averaged to minimize measurement noise. In theillustrations which follow, The “Acquisition Parameters” method of theinstrument is set with a sampling interval of 1 and a detectionthreshold of 0.2. The “Multisampler-SP” method of the instrument setsthe platen temperature (100° C. for the examples herein). Two othertemperatures (115° C. and 125° C.) are automatically set. TheMultisampler-SP method is also used to set the parameters in Table 8 tomeasure aroma intensity. TABLE 8 AromaScan ® Settings SampleEquilibration Time: 5 minutes Vial Size: 22 ml Mix Time:  0 Mix Power: 1 Relative Humidity: 10% Sampling Time: 4 minutes Wash Time: 5 minutesData Collection Time (minutes): 19 Time Between Injections 20 (minutes):

[0177] In the recognition window, start and end are set at 1. Inaddition to the foregoing, the “Vial Pressurization Control” is set at20 kPa, the “Vial Needle Flow” is set at 50 ml/min nitrogen; “TransferLine Flow” across the sensors, between, before and after samples is setat 150 ml/min. All gas flows are for dry nitrogen.

[0178] A response of each of the 32 sensors of the AromaScan® machine isintegrated over a time interval of 55 - 150 seconds. The initial 55seconds is allowed to let humidity/moisture exit the system to a greatextent before integration is started. The 150 second integration endtime was chosen to allow the sensor signals to return to baseline, atwhich time all significant signal has been integrated. The varioussignals seen after 150 seconds are insignificant in terms of the odormeasurement, as can be seen from FIG. 5. FIG. 5 is a plot of sensorresponse vs. time for each of the 32 sensors of the Aroma Scan device,where individual responses are shown as various lines on the diagram.

[0179] Using the foregoing procedure, 2.0 grams of compounded polymerpellets are weighed and placed in the 22 ml, crimp top, septum cappedvials and analyzed automatically by the instrument. There is shown inFIG. 6 the results for various extruded polypropylene/mica pellets. Thedata points shown on FIG. 6 are actually the response integrals for aparticular sensor.

[0180] The abscissa on FIG. 6 indicates each of the 32 elements; whilethe ordinate is the time-integrated response of the correspondingelement in arbitrary units. There is shown as curve A the (integrated)sensor responses for the standard sample prepared as above. As notedbefore, this sample has a relative aroma intensity index of 1.0 bydefinition. There is also shown a sample prepared in accordance with thestandard sample procedure except that polypropylene was substituted forcalcium carbonate at curve B as in the “high odor” compositions of theKansas State Trials discussed above in connection with Examples 12 - 17.As can be seen, this composition has a relative aroma intensity index ofabout 1.6; or in other words, its response integrals are on average 1.6times those of the standard sample. There is also shown on FIG. 6 athird curve (C) representative of more preferred compositions preparedin accordance with the present invention. Curve C represents acomposition prepared in accordance with Examples 28 through 30 below(Table 11) wherein the relative aroma intensity index is less than about0.7 which means its response integrals are on average less than 0.7times those of the standard sample.

[0181] Through the use of an automated instrument, the aroma intensityof the melt-compounded pelletized composition can be reduced to a singlevalue. While the foregoing sets forth a particular and preferred methodof determining the relative aroma intensity index, it may also bepossible to employ other instruments consistent with this protocol sincesuch instruments are readily available. If such alternative instrumentis employed the standard composition detailed above should be used toensure that calibration is proper. As noted, the standard compositionhas a RAII of 1.0 while a composition prepared substitutingpolypropylene for the calcium carbonate of the standard composition hasa RAII of about 1.6 or above and a composition prepared in accordancewith Examples 28 through 30 should have a RAII of 0.7 or less. By usingthese multiple reference points, the relative aroma intensity index isalways readily determined by one of skill in the art.

EXAMPLES 18 - 26

[0182] A series of resin compositions and sheet products were preparedin accordance with the discussion above and characterized by C8/C7ketone ratio and odor panel testing. Variables included calciumcarbonate addition, process atmosphere (air or nitrogen) and processmelt temperature. Results appear in Table 9 for examples 18 through 26.TABLE 9 CaCO₃ Effect of Process Conditions and Compositions on Odor ofPP/Mica Composites Odor Panel Data Type “Scorched” (Banbury or ProcessC₈/C₇ Sustained Odor Profile Extruded Atmosphere CaCO₃ Process MeltKetone (Total Component Example Sheet) (Air/N₂) (Yes/No) TemperatureRatio Intensity) Intensity 18 Brabender Air Yes 370° F. 0.055 2.0 0Banbury Compounded 19 Brabender Air Yes 460° F. 0.6 4.0 5.0 BanburyCompounded 20 Sheet N₂ Yes 460° F. 0.3 21 Brabender Air Yes 460° F. 0.64.0 5.0 Banbury Compounded 22 Sheet Air Yes 370° F. 0.15 2.0 0 23 SheetAir No 370° F. 13 6.0 4.5 24 Sheet Air Yes 400° F. — 5.0 2.5 25 SheetAir No 460° F. 0.9 8.0 3.5 26 Sheet Air Yes 460° F. 0.7 2.0 0

[0183] The resins of Examples 18, 19, and 21 were prepared on aBrabender device (C. W. Brabender, model EPL2V5502) with a Banbury mixhead (model R.E.E.6, 230v, 11a) with a mixing time of 5-10 minutes

[0184] The sheet samples, Examples 20 and 22 through 26, were preparedfrom precompounded resin pellets extruded under the conditions shown inTable 10. TABLE 10 Sheet Extrusion Conditions for PP/Mica Pilot ExtruderCONDITIONS ACTUAL SET POINT Barrel Zone 1 (° F.) 354-378 360-375 BarrelZone 2 (° F.) 366-410 370-410 Barrel Zone 3 (° F.) 371-460 370-460Adapter temp (° F.) 359-460 370-460 Feed Block Temp (° F.) 370-468370-460 Die Zones 1-3 temps (° F.) 368-462 370-460 Extruder RPM 110 110Drive Amperes 15-23 — Melt Pressure (psi) 1050-1850 — Die Pressure (psi)745-910 — Line Speed (FPM) 8.25-9.74 — Chill roll temp. (° F.) 130 —

[0185] The odor of PP/mica composites (pellets or sheet) is affected bytemperature, atmosphere, and by the addition of a basic filler such asCaCO₃. The C8/C7 ketone ratio is consistent with the odor panel data andshows that offensive odor components decrease with:

[0186] Using lower processing temperatures

[0187] Using a base such as CaCO₃ as a buffering agent

[0188] Processing under inert atmosphere such as N₂.

EXAMPLES 27-30

[0189] Particularly preferred, low odor compositions are prepared by wayof a sequential process in a Banbury mixer at relatively lowtemperatures. A typical Banbury apparatus is shown schematically in FIG.7. An apparatus 110 includes generally a feed hopper 112 provided with afeed ram 114 coupled to a weight cylinder 116 which may be varieddepending on the force required for a particular process. Feed hopper112 has a lower portion 118 which communicates with a mixing chamber 120provided with a pair of rotors 122, 124. The material is supplied tohopper 112 through a charging door indicated at 126, and/or fed througha feed port located at 128. Chamber 120 is further provided with adischarge door 130 which is positioned above a conveyor indicated at132. Such apparatus is well known for compounding thermoplasticcompositions.

[0190] A conventional non-sequential process is operated as follows: (a)discharge door 130 is closed; (b) ram 114 is drawn up; (c) theingredients are added; (d) the ram is lowered and the rotors activated;(e) mixing is complete when a combination of temperature and work hasbeen achieved (power draw on mixer motor falls off); (f) at which pointthe discharge door is opened and the batch is gravimetrically suppliedto a conveyor; and finally (g) the batch is conveyed to a single screwextruder and pelletized. The apparatus melts the polymer through sheargenerated by the rotors and walls against the components being mixed.One may rely on shear (that is, mechanical work) to soften thethermoplastic components or apply some auxiliary heat directly either inthe feed hopper or the chamber through the use of heating coils,infrared devices, steam jacketing and the like, or, alternatively,preheating the polymer externally prior to feeding.

[0191] It has been found that melt compositions prepared in a sequentialBanbury process exhibit superior stiffness as measured by flexuralmodulus properties and low odor. In a sequential process in accordancewith the invention, two feed steps are used in order to minimize thetime heated or molten polypropylene is in contact with the mica as willbe explained in connection with FIGS. 7 and 8.

[0192] In a first, melt mix step, door 130 is closed and ram 114 isdrawn up. Polypropylene, polyethylene, titanium dioxide, other pigmentsand the like are added. Ram 114 is lowered and the rotors 122, 124 arerotated to shear the material. A typical power curve (at constant rotorspeed) for amperage supplied to the mixing motors for the inventivesequential process is shown in FIG. 8, a plot of amperage versus time inhours:minutes:seconds.

[0193] When the pair of rotating rotors are first started in the meltmix step, the current draw is indicated at point P1 on FIG. 8 where itcan be seen power applied to the polymer is quite high. The current drawreaches a maximum at about P2 where the polymer begins to softenrapidly. At P3 after a minute or two the current draw is at a minimumwhile the components are being mixed when the polymer is in a softenedstate. Mica and calcium carbonate may then be added simultaneously in amica addition step as will be detailed below.

[0194] After the polymer is softened, ram 114 is again drawn up and themica and calcium carbonate may be added at the time corresponding to P4on the diagram. The material may be added through a door 126 or feedport 128. The current draw at constant rotor speed again increases asshown at P5 and eventually begins to decay as shown at P6 and P7. Morepreferred is to add the mica and calcium carbonate mixture at about thetime corresponding to P2 prior to complete softening of the resin.Alternatively, polypropylene may be externally preheated to about 240°F. or so (along with the mixing chamber to the same temperature) and allof the ingredients are simultaneously added for maximizing processthroughput. Preferred drop batch temperature at the end of Banbury meltcompounding, that is, maximum melt processing temperature for this stepis up to about 425 degrees Fahrenheit. At the time corresponding to P7,the door may be opened and the batch of material (a batch size is about200 pounds) conveyed to an extruder to be pelletized. TABLE 11Comparison of Compounding Processes Compound Flexural Relative AromaCOMPOUNDING Modulus 9″ Plate Intensity index PROCESS (Tangent), PSIRigidity (g/0.5″) (Compound) Twin Screw 718,000 417 1.0 Example 27Banbuxy 591,000 378 0.59 (non-sequential) Example 28 Banbury(sequential, 708,000 416 0.65 1 min. pre-heat) Example 29 Banbury635,000 352 0.62 (Sequential, 2 min. premelt) Example 30

[0195] Table 11 shows compound flexural modulus (as measured by ASTMmethod D 790-95a), corresponding plate rigidity, and aroma intensityindex on four indicated compounding processes designated as examples27 - 30. In the to case of twin-screw (Example 27), high modulus isobtained but with higher odor with relatively low throughput, in therange of 900 lb/hr, which is less than half the output of Banburycompounding processes (utilizing a Stewart-Bolling Banbury Mixer withbatch sized in the range of 150-200 lb) listed herein. In the case ofnon-sequential Banbury process, low modulus is obtained withcorresponding low plate rigidity with lower odor and high throughput. Inthe last two cases corresponding to sequential Banbury processesdesignated as “1 min. pre-heat” and “2 min. pre-melt”, the short 1minute preheat case (Example 29) is preferred because it gives highcompound modulus and high plate rigidity (comparable to twin screw case)with benefits of both low odor and high throughput, in excess of 2000lb/hr.

[0196] The twin screw formulation in the above table contains PPI30%mica/ 10% CaCO3 with 2.5% coupling agent (maleic anhydride modified PPgrade Aristech Unite NP -620) and no polyethylene. The formulationcorresponding to all three listed Banbury processes in above tablecontain PP/30% mica/10% CaCO3/0.5% TiO2/4%LLDPE with no coupling agentwhere such ingredients have the following sources and grades:Mica=Franklin Minerals L-140, CaCO₃=Huber Q325, PP=Exxon EscorenePP4772, LLDPE=Novapol Novachemical G1-2024A.

[0197] The Banbury “non-sequential” case (Example 28) in Table 11corresponds to adding all ingredients together with a total compoundingtime of about 4.5 minutes followed by conversion of the batch (havingtemperature of 430° F.) to pellets using a continuous 10″ single screwextruder equipped with one 30 mesh and one 20 mesh screen, and anunderwater pelletizing die assembly, with a pelletizing temperature inthe range of 455-470° F.

[0198] The Banbury “sequential 2 min premelt” case (Example 30) in Table11 corresponds to a 2 minute period for melting the PP/LLDPE mixture (inthe presence of CaCO₃ and TiO2) to a maximum temperature of about 350°F., followed by adding mica and thereafter mixing for a period of about105 sec to achieve a batch temperature of about 430° F., followed byconversion to pellets with a pelletizing temperature of about 460° F.The Banbury “sequential, 1 min pre-heat” case (Example 29) in Table 11corresponds to about a 1 minute period for presoftening the PP/PEmixture (in the presence of TiO2, or alternatively adding the TiO₂ withthe mica and calcium carbonate) to a maximum temperature of about 260°F., followed by adding the mica/CaCO₃ mixture and thereafter mixing toachieve a batch temperature of about 425° F., followed by conversion topellets with a pelletizing temperature of about 425° F. In thispreferred mode, it has been found that polymer preheating aids inpreserving compound stiffness (required for rigid articles ofmanufacture) and intimate contact of mica with odor suppressing agent(CaCO₃) aids the production of low odor material.

[0199] Pellets from the above mentioned Banbury compounding processeswere subsequently extruded at 370° F. as cast sheets in the range of17-18 mil. Sheet line conditions also included a screw RPM value of 100,a chill roll temperature of about 130° F., drive amperage value of about22, melt pressure of about 2000 psi, die pressure of about 970 psi, anda line speed of about 7 ft/min. Plates were subsequently vacuumthermoformed using a female mold and trimmed and tested for rigidity.

EXAMPLES 31 - 41

[0200] Extruded mica filled polypropylene sheets prepared as describedin Examples 1 through 8 were characterized with respect to surface glossand roughness. Table 12 shows 75 degree gloss and Parker Roughness(airflow method) data for an extruded mica filled polypropylene sheetversus same properties for the food contact (air) side of vacuum formed10.25 inch plates produced according to condition (B) of FIG. 2 usingthe same sheet formulation. The unique thermally induced micronodularsurface is characterized by significant decrease in gloss andsignificant increase in roughness as shown in the two photomicrographsin FIGS. 9A and 9B, which results in a stoneware or pottery likeappearance with aesthetic appeal. (The Parker Roughness method isdescribed above). The upper photomicrograph of FIG. 9A is of athermoformed plate surface, while the lower photomicrograph of FIG. 9Bis of sheet.

[0201] The photomicrographs of FIGS. 9A and 9B were obtained from a10×15 mm piece cut out of a plate bottom. The sheet sample was mountedwith surface of interest up on a specimen stub, and coated withgold/palladium. The stub was placed in a JEOL 840A Scanning ElectronMicroscope (SEM). Photomicrographs of the samples were taken at 75xmagnification, 30 degree tilt, 39 mm working distance at 3 kv. TABLE 12GLOSS AND ROUGHNESS PROPERTIES OF THE FOOD CONTACT SIDE OFPOLYPROPYLENE/MICA/TIO₂ PLATE SURFACE VERSUS NEAT EXTRUDED SHEET GLOSSPARKER ROUGHNESS EXAMPLE (75 DEGREES) * (MICRONS) 31 (Plate) 22.4 13.4132 (Plate) 30.6 14.05 33 (Plate) 24.8 14.89 34 (Plate) 24.3 14.24 35(Plate) 24.5 12.48 PLATE AVERAGE 25.3 ± 3.1 13.8 ± 0.9 36 (Sheet) 45.75.92 37 (Sheet) 47.2 7.43 38 (Sheet) — 5.89 39 (Sheet) — 6.35 40 (Sheet)— 5.84 41 (Sheet) — 8.15 SHEET AVERAGE 46.5 6.6 ± 0.97

[0202] As shown in Table 12, the food contact side is rougher asevidenced by increased roughness and decreased gloss relative to theneat extruded sheet. The rough appearance is desirable for purpose ofcreating the micronodular surface giving the container and plate astoneware or pottery-like look.

EXAMPLES 42 - 43

[0203] Mica filled polypropylene sheets were successfully vacuumthermoformed into 12 oz. oval microwave containers, whereby the base wasproduced using mode (B) of FIG. 2 and the lid was produced using mode(A) of FIG. 2. In contrast, attempts to form unfilled polypropylenesheet into the same container were not successful.

EXAMPLES 44 - 46

[0204] Sheet rolls (17.5 wide), at three calipers were extruded asdescribed in Examples 1 through 8 in connection with FIG. 1. Table 13summarizes the PP/40% mica material and process conditions. Table 14summarizes the PP/40% mica sheet properties. TABLE 13 PP/Mica ExtrusionProcess Conditions Summary Barrel Barrel Barrel Adaptor Feed Plate Zone1 Zone 2 Zone 3 Temp.(F.) Block Line Die Zone 1 Die Zone 2 Die Zone 3Size Temp.(F.) Temp.(F.) Temp.(F.) Actual/ Temp. Speed Temp.(F.)Temp.(F.) Temp.(F.) (in.) Actual/Set Actual/Set Actual/Set SetActual/Set (fpm) Actual/Set Actual/Set Actual/Set 11 395/395 452/425475/475 470/470 470/470 9.27 470/470 469/470 470/470 10 376/375 410/410431/430 430/430 430/430 8.32 430/430 430/430 430/430  9 375/376 410/410434/430 430/430 430/430 8.07 430/430 430/430 430/430 Plate Screw MeltDie Chill Roll Size RPM Drive Pressure Pressure Temp.(F.) (in.)Actual/Set Amperes (psi) (psi) Actual/Set 11 125 18.3 1387 694 130/13010 130 19.3 2012 737 130/130  9 132 24.2 2112 686 130/130

[0205] TABLE 14 PP/Mica Sheet Property Summary Plate Size Overall BasisWeight - Avg. (in.) Overall Caliper - Avg. (mil) (lb./3000 ft.{acuteover ( )}2) 11 18.46 ± 0.36  308.07 ± 13.72 10 17.20 ± 0.10 288.80 ±9.89  9 16.94 ± 0.10 268.11 ± 7.50

EXAMPLE 47 - 49

[0206] Plates from sheet specifications set forth in Examples 31 - 41were produced using 1 -up water cooled female molds (with pressurebox/vacuum assembly), followed by matched metal punch trimming. Moldtemperature was 70° F., while sheet temperatures for the 9, 10, and 11inch plate runs were respectively 300° F., 310° F., and 295° F. The 9and 10 inch plates were produced at 20 cycles/minute while the bulk ofthe 11 inch plates were made at 25 cycles/minute.

[0207] Oven temperature control on the commercial machine was good dueto the combination of top quartz heaters and bottom calrod heaters withproper zoning. In general, higher temperatures produce moremicronodularity at the expense of more pronounced sheet sag andwrinkling while low temperatures tend to reduce sag at the expense ofdiminished stoneware or pottery-like appearance.

[0208] Best results (i.e., micronodular matte eating surface without“webbing” or wrinkling) were obtained by increasing the top oventemperature by 3-5° F. and decreasing the bottom by a correspondingamount. This ability to selectively control oven temperature in effectfacilitated determination of the preferred process temperature window ofPP/mica sheets.

EXAMPLES 50 - 54

[0209] Sheets and plates were prepared as illustrated in Examples 1through 8 and FIGS. 1 and 2. Table 15 shows sheet extrusion and formingconditions. FIGS. 10 and 11 respectively, show gloss and plate rigidityversus mica level (at constant mica/TiO₂ ratio). TABLE 15Extrusion/Forming Conditions Barrel Zone 1 375° F. Barrel Zone 2 410° F.Barrel Zone 3 430° F. Adaptor 430° F. Feedblock 430° F. Die Zones 1/2/3430° F. RPM 130 Chill Roll 130° F. Target Sheet Caliper 18.3 mil SheetWidth 18.0 inches Comet Former Top Heater 20% Comet Former Bottom Heater35% Comet Former Time 50-60 seconds Plate Diameter 11 inch

EXAMPLES 55 - 62

[0210] Commercial sheet extrusion runs of several mica filledpolypropylene formulations were conducted. These sheets suitably have abasis weight of about 200 to 950, per 3000 square foot ream, preferablyabout 200 to 400 per 3000 square foot ream. These mica filledpolypropylene sheets had a mica content in the range of 25 to 35 weightpercent.

[0211] The extrusion of coupled mica and polypropylene blends wasconducted on a 6″ commercial extruder line. The extruder was an Egan24/1 LAD with a general purpose screw. The die was an Extrusion Die Inc.52″ coat hanger type. The stack conditioning rolls were top polishedchrome, middle matte (40 RA surface), and bottom polished chrome. Thematte chill roll assisted with the formation of the micronodular surfaceduring thermoforming of the sheet with beneficially improving breadth offorming temperature window in contrast with non-matted smooth sheets.The differences between surfaces of the various sheets and plates madetherefrom may be better appreciated by reference to FIGS. 12 and 13hereof. FIG. 12A is a scanning electron photomicrograph of surface A ofTable 16, while FIG. 12B is a scanning electron photomicrograph ofsurface B of Table 16. FIG. 13A is a scanning electron photomicrographof surface G of Table 16 and FIG. 13B is a scanning electronphotomicrograph of surface H of Table 16.

[0212] The roughness of various surfaces is compared in Table 16 below.TABLE 16 Roughness and Gloss Properties of PP/30% Mica Extruded Sheetsand Thermoformed Plates Sheet Thermoforming Temperature Parker RoughnessSurface (° F.) (microns) Gloss (75%) A —  8.56 ± 0.39  4.99 ± 0.11 B —15.82 ± 0.74  8.05 ± 0.30 C 305 13.14 ± 0.74 14.3 ± 1.0 D 300 11.74 ±0.86 11.6 ± 1.0 E 292 12.10 ± 0.82 11.7 ± 1.0 F 265 10.63 ± 0.68 8.20 ±0.6 G — 6.17 82.10 H — 5.14 80.75

[0213] (A) Matte extruded sheet having top matte side.

[0214] (B) Extruded sheet (A) - bottom side opposite to matte side

[0215] (C, D, E, F) Plate - eating side corresponding to top matte sideof (A)

[0216] (G) Non-matte extruded sheet - top side (no matte roll)

[0217] (H) Non-matte extruded sheet - bottom side (no matte roll)

[0218] For a non-matte extruded sheet, usually plate gloss and plateroughness are inversely related (e.g., high gloss corresponds to lowroughness and vice versa as demonstrated in prior art data generallyobtained). In that case, achieving desirable micronodular texture iswithin a temperature range (about 295° F. to 305° F.) where above thisrange the forming process is sag limited while below this range theplate exhibits poor micronodular character as manifested by high glossand low roughness.

[0219] The use of a matte roll in the chill roll stack portion of theextrusion process effectively broadens the commercially attractivethermoforming process temperature range (about 265° F. to 305° F.).Specifically, plates having acceptable surface micronodularity can beformed at lower temperatures, whereby the decrease in plate roughness iscompensated by an unexpected decrease in plate gloss using sheet surface(A). This beneficial increase in plate forming temperature window fromabout 10° F. to about 40° F. is brought about by imparting a mattesurface finish to the extruded sheet.

[0220] The extruded sheet used in the suitable forming and thermoformingprocess, or the preferred thermoforming process as shown in FIG. 2 has athickness of about 0.010 to 0.080 inches, suitably 0.010 to 0.030inches, and preferably 0.015 to 0.25 inches. Suitable mica fillerloading level in the extruded sheet is in the range of 25-30 weightpercent, whereby mica flake aspect ratio is in the range of 30-300, morepreferably 80-120, with particle size range of about 50-500 microns.

[0221] By matte finishing one side of the sheet using matte roll, thecommercial thermoforming was suitably conducted at a broader temperaturewindow of about 265° F. to 305° F. while without matte finishing, thethermoforming using the same commercial equipment was conducted at atemperature of about 295° F. to 305° F.

[0222] The runs on commercial equipment using PP/30% mica and PP/25%mica formulations showed that the thermoforming temperature window rangehas been expanded from about 10° F. (previous trial) to as high as about35° F. This is primarily due to the fact that we beneficially used amatte roll in the chill roll stack during the extrusion process. Thisgave a smooth matte finish for the air side of the sheet (i.e., plateeating surface) while the rougher bottom side was in contact with thesandblasted mold side during the forming process. Use of matte sheet, inturn, enabled forming at lower temperatures (which is good for sagavoidance) without much loss in micronodularity. Specifically, theforming window was in the range of 265° F. to about 300° F. to 305° F.where best balance of process stability and product appearance/texturewas seen at about 280° F. to 290° F.

[0223] Preferred Articles

[0224] The sheet of the present invention is suitably formed into platesor bowls having a circular configuration. These articles of manufacturemay also be square or rectangular in shape having angular corners, suchas found in a tray. Further, additional shapes such as triangular,multi-sided, polyhexal, etc., are contemplated including compartmentedtrays and plates as well as oval platters. In each contemplatedembodiment, all corners are rounded or curved with a preferred pluralityof embodiments of the present invention being depicted in FIGS. 14through 33. The various embodiments shown in FIGS. 14 through 33, whileillustrative of the present invention, are not intended to limit theinvention and those of skill in the art may make changes withoutchanging the essential characteristics of the invention. Thesecontainers may also have other features such as ridges, emboss, anddeboss patterns suitable for enhancing the properties of the containersof this invention. These container's bottom sections may have a convexcrown to improve stability and reduce rocking during use.

[0225] Throughout the following description, each of the dimensions arereferenced with respect to a given diameter D which, in accordance withthe present invention as illustrated in FIGS. 14 through 17 isapproximately 8.75 inches. However, the particular diameter of thecontainer is not a critical limitation and is only set forth herein byway of example. It is the relationship between the various portions ofthe rim configuration which are essential.

[0226] The planar inner region in accordance with the illustratedembodiment of a plate in FIGS. 14 through 17 has a radius X1 which isequal to approximately 0.3 D-0.4 D and preferably 0.348 D. This plate isdescribed generally in U.S. Pat. No. 5,326,020 the disclosure of whichis incorporated herein by reference. Adjoining an outer periphery of theplanar inner region 150 is a sidewall portion 152 including annularregion 154 having a radius of curvature equal to approximately 0.05D-0.06 D and preferably 0.0572 D with the center point thereof beingpositioned a distance Y1 from the planar inner region 150. Includedangle 156 of the annular region 154 is from about 400 to about 700 andpreferably about 60°-65° or approximately 620. Adjoining the peripheryof the annular region 154 is the first frusto-conical region 158 whichslopes upwardly at an angle A1 with respect to the vertical from about20° to about 35° and preferably about 25°-30° or approximately 27.5°.Additionally, the frusto-conical region 158 is adjacent to the arcuateannular region 160 which includes a radius of curvature in the range of0.015 D to 0.03 D and preferably approximately 0.024 D with the centerpoint thereof being positioned a distance Y2 from the planar innerregion 150. The included angle 162 of the arcuate annular region 160 mayrange from about 61° to about 82° and is preferably 66° to 77° or about73°. The second portion 164 of the arcuate annular region 160, that isthe distal portion of the arcuate annular region 160, is positioned suchthat a line tangent to the curvature of the arcuate annular region 160at the second portion 164 slopes downwardly and outwardly at an angle ofapproximately 0° to 12°.

[0227] The combination of the annular region 154 and arcuate annularregion 160 should combine to position the second portion 164 of thearcuate annular region 160 in the manner set forth herein above. Thatis, the included angle 156 of the annular region 154 when combined withthe included angle 162 of the arcuate annular region 160 with the firstfrusto-conical region 158 spanning therebetween, positions the secondportion 164 of the arcuate annular region 160 in a manner such that asecond frusto-conical region 166, which extends substantiallytangentially from the distal end of the second portion 164 of thearcuate annular region 160 extends outwardly and downwardly at an angleof about 0° to 12°. The second frustro-conical region 166 is of a lengthin a range from about 0.03 D to about 0.05 D and is preferably 0.04 D.Because the second frusto-conical region 166 extends substantiallytangentially from the second portion 164 of the arcuate annular region160, the second frusto-conical region 166 extends outwardly anddownwardly at an angle A3 in the range from approximately 0° to 12° withrespect to a horizontal plane formed by the planar inner region 150.

[0228] Adjoining an outer periphery of the second frusto-conical region166 is the lip 168 which is in the form of yet another frusto-conicalregion which extends outwardly and downwardly from the secondfrusto-conical region 166. The lip 168 is of a length of at least 0.005D and is preferably approximately 0.010 D. Further, the lip ( 168 )extends at an angle A2 of no more than 45° from vertical, preferablyapproximately 15° to 30° with respect to the vertical plane.

[0229] At the transition between the second frusto-conical region 166and the lip 168 is a transition region 170. The transition region 170includes a radius of curvature R3 which is in the range of about 0.008 Dand 0.01 D and is preferably approximately 0.0092 D with the centerpoint thereof being positioned a distance Y3 from the planar innerregion 150. Additionally, the transition region 170 has an includedangle A4 of approximately 48° to 70°.

[0230] The plates disclosed in FIGS. 18 through 20 generally have thedimensions of the plates disclosed in U.S. Pat. No. 5,088,640 which isincorporated herein by reference in its entirety. These containers mayhave other features such as ridges, emboss, and deboss patterns suitablefor enhancing the properties of the containers of this invention. Thereis shown in FIGS. 18 through 20 a plate having a planar center includingan outer peripheral surface. The planar center forms a bottom for theplate. An outwardly projecting sidewall includes a first rim portionjoined to the outer peripheral surface of the planar center and a secondrim portion joined to the first rim portion. The first and second rimportions form a sidewall of the plate. A third rim portion is joined tothe second rim portion of the outwardly projecting sidewall and a fourthrim portion is provided for forming an outer edge of the container. Thefirst rim portion is joined to the peripheral surface of the planarcenter at an angle having a second predetermined radius. The third rimportion is joined to the second rim portion at an angle having a thirdpredetermined radius. The fourth rim portion is joined to the third rimportion at an angle having a fourth predetermined radius. The four radiias well as the four included angles are selected for enhancing rigidityof the plate as compared to a container made from the same material byother means as is further described below.

[0231] Illustrated in FIGS. 18-20, there is a plate 180 which includes aplanar center 182 which, in turn, includes an outer peripheral surface184. This center region 182 may have a slight convex crown to improveplate stability during use. The planar center 182 forms a bottom for theplate 180. An outwardly projecting sidewall 186 includes a first rimportion 188 which is joined to the outer peripheral surface 184 of theplanar center 182. A second rim portion 190 is joined to the first rimportion 188. The first rim portion 188 and the second rim portion 190form the outwardly projecting sidewall 186 which forms the sidewall ofthe plate 180. A rim 192 includes a third rim portion 194 which isjoined to the second rim portion 190 of the outwardly projectingsidewall 186. A fourth rim portion 196 is joined to the third rimportion 194. The fourth rim portion 196 forms the outer edge of theplate 180.

[0232]FIG. 20 illustrates a partial cross-sectional view of a plate,diameter D, according to the present invention. The plate 180 defines acenter line 204. A base or bottom-forming portion 200 extends from thecenter line 204 to an outer peripheral surface 202.

[0233] From the center line 204 a predetermined distance X12 extendstoward the outer peripheral surface forming portion 202. A distance Y12extends a predetermined distance from the base or bottom-forming portion200 upwardly therefrom. A radius R12 extends from the intersection pointof the distance X12 and Y12 to form a first rim portion 206 of theoutwardly projecting sidewall 205. The first rim portion 206 is definedby an arc A12 which extends from the vertical line defined at the outerperipheral surface 202 to a fixed point 210. The arc A12 may beapproximately 60°.

[0234] A distance X22 extends from the center line 204 to apredetermined point. A distance Y22 extends from the base orbottom-forming portion 200 of the plate 180 downwardly a predetermineddistance. A radius R22 extends from the intersection of the lines X22and Y22 to form a second rim portion 208 of the sidewall 205. The radiusR2 extends from the first fixed point 210 to the second fixed point 212through an arc A22. The arc A22 may be approximately 4°.

[0235] A distance X32 extends from the center line 204 to apredetermined distance. A distance Y32 extends from the base orbottom-forming section 200 of the plate 180 to project upwardly apredetermined distance. A radius R32 extends from the intersection ofthe lines X32 and Y32 to form the third rim portion 214 of the rim 216.The radius R32 extends from the second fixed point 212 to a third fixedpoint 218. An arc A32 is formed between the second fixed point 212 andthe third fixed point 218 to extend a predetermined distance. The arcA32 may be approximately 55°.

[0236] A distance X42 extends a predetermined distance from the centerline 204. Similarly, a distance Y42 extends from the base orbottom-forming section 200 of the plate 180 to project outwardly. Aradius R42 extends from the intersection of the lines X42 and Y42 toform a fourth rim portion 217 of the rim 216. An arc A42 is formedbetween the third fixed point 218 and a fourth fixed point 220 atdiameter D from the center line. The arc A42 may be approximately 60°. Asection 220 forms the outer edge of the plate.

[0237] The container made according to the present invention may haveany particular size as desired by the user so long as the relativeprofile dimensions are maintained. More specifically, ovals, rectangleswith rounded corners and other shapes may be made having this profile.In various embodiments of the present invention the container may be a9-inch or 11-inch plate with profile coordinates as illustrated in FIGS.18 through 20 having the dimensions, angles, or relative dimensionsenumerated in Tables 17 through 19. TABLE 17 Dimensions and Angles For9″ Plate DIMENSION and ANGLES VALUE (inches or degrees) R12 0.537 X123.156 Y12 0.537 R22 2.057 X22 5.402 Y22 0.760 R32 0.564 X32 4.167 Y320.079 R42 0.385 X42 4.167 Y42 0.258 A12 60.00° A22 4.19° A32 55.81° A4260.00° D 9.00 BOTTOM CONVEX CROWN 0.06

[0238] TABLE 18 Dimensions and Angles For 11″ Plate DIMENSION/ANGLESVALUE (inches or degrees) R12 0.656 X12 3.857 Y12 0.656 R22 2.514 X226.602 Y22 0.929 R32 0.689 X32 5.093 Y32 0.097 R42 0.470 X42 5.093 Y420.315 A12 60.00° A22 4.19° A32 55.81° A42 60.00° D 11.00 BOTTOM CONVEXCROWN 0.06

[0239] TABLE 19 Dimensions For 9 and 11 INCH PLATE DIMENSION RATIOVALUES (Dimensionless or degrees) OR ANGLE PREFERRED MINIMUM MAXIMUMR12/D 0.060 0.045 0.075 X12/D 0.351 0.280 0.420 Y12/D 0.060 0.045 0.075R22/D 0.228 0.180 0.275 X22/D 0.600 0.480 0.720 Y22/D 0.084 0.065 0.100R32/D 0.063 0.050 0.075 X32/D 0.463 0.370 0.555 Y32/D 0.009 0.007 0.011R42/D 0.043 0.034 0.052 X42/D 0.463 0.370 0.555 Y42/D 0.029 0.023 0.035A12 60.00° 55.00° 75.00° A22 4.19° 1.00° 10.00° A32 55.81° 45.00° 75.00°A42 60.00° 45.00° 75.00°

[0240] Salient features of the plate illustrated in FIGS. 18 through 20generally include a substantially planar center portion (which may becrowned as noted above and illustrated throughout the various figures)with four adjacent rim portions extending outwardly therefrom, each rimportion defining a radius of curvature as set forth above and furthernoted below. The first rim portion extends outwardly from the planarcenter portion and is convex upwardly as shown. There is defined by theplate a first arc A12 with a first radius of curvature R12 wherein thearc has a length S1. A second rim portion is joined to the first rimportion and is downwardly convex, subtending a second arc A22, with aradius of curvature R22 and a length S2. A third, downwardly convex, rimportion is joined to the second rim portion and subtends an arc A32.There is defined a third radius of curvature R32 and a third arc lengthS3. A tangent to the third arc at the upper portion thereof issubstantially parallel to the planer center portion as shown in FIG. 20.A fourth rim portion is joined to the third rim portion, which is alsodownwardly convex. The fourth rim portion subtends a fourth arc A42 witha length S4, with a radius of curvature R42.

[0241] The length of the second arc, S2 is generally less the length ofthe fourth arc S4, which, in turn, is less than the length S1 of thefirst arc A12. The radius of curvature R42 of the fourth arc is lessthan the radius of curvature R32 of the third rim portion, which inturn, is less than radius of curvature R22 of the second rim portion.The angle of the first arc, A12 is generally greater that about 55degrees, while, the angle of the third arc, A32 is generally greaterthan about 45 degrees as is set forth in the foregoing tables. The angleof the fourth arc A42 is generally less than about 75 degrees and morepreferably is about 60 degrees.

[0242] Typically, the length S1 of arc A12 is equivalent to the lengthS3 of arc A32 and R12 of the first rim portion is equivalent in lengthto the radius of curvature R32 of the third rim portion.

[0243] Generally speaking, the height of the center of curvature of thefirst arc (that is the origin of ray R12) above the central planarportion is substantially less than, perhaps twenty five percent or soless than, the distance that the center of curvature of the second rimportion (the origin of ray R22) is below the central planar portion. Inother words, the length Y12 is about 0.75 times or less the length Y22.

[0244] So also, the horizontal displacement of the center of curvatureof the second rim portion from the center of curvature of the first rimportion is at least about twice the length of the first radius ofcurvature R12. The height of the center of curvature of the third rimportion above the central planar portion is generally less than theheight of the center of curvature of the fourth rim portion above theplane of the central planar portion. The horizontal displacement of thecenter of curvature of the second rim portion is generally outwardlydisposed from the center of curvature of the third and fourth rimportions.

[0245] A final noteworthy feature of the plate of FIGS. 18 through 20 isthat the height of the center of curvature of the third rim portionabove the planar central portion is less than about 0.75 times theradius of curvature R42 of the fourth rim portion; while the height ofthe center of curvature of the fourth rim portion above the plane of thecentral portion is at least about 0.4 times the first radius ofcurvature R12.

[0246] Yet other embodiments of this invention include trays which haveeither the DIXIE(g Superstrong profile as illustrated in FIGS. 21through 24 and/or described in U.S. Pat. No. 5,326,020 assigned to theassignee of the present invention and incorporated herein by referenceinto this application. These trays may have other features such asridges, emboss, and deboss patterns suitable for enhancing theproperties of the trays of this invention. Throughout the followingdescription of FIGS. 21 through 24, each of the dimensions arereferenced to either the length D1 or the width D2, which areapproximately 10.90 and 8.00 inches respectively. D1 is larger than orequal to D2. However, the particular length and width of thesecontainers is not a critical limitation and is only set forth herein byway of example. It is the relationship between the various portions ofthe rim configurations which are essential. The planar inner region 101in accordance with the illustrated embodiment in FIGS. 21 A through 24,has a length 1X which is equal to approximately 0.3 D1 to 0.4 D1 and 0.3D2 to 0.4 D2 and preferably 0.354 D1 and preferably 0.342 D2. Adjoiningan outer periphery of the planar inner region 230 is a sidewall portion232 including annular region 234 having a radius of curvature equal toapproximately 0.02 D1 to 0.03 D1 and 0.025 D2 to 0.035 D2 and preferably0.023 D1 and 0.031 D2 with the center point thereof being positioned adistance Y1 from the planar inner region 230. Included angle 236 of theannular region 234 is from about 40° to about 80° and preferably about65° to 75° or approximately 69°. Adjoining the periphery of the annularregion 234 is the first frusto-conical region 238 which slopes upwardlyat an angle A1 with respect to the vertical from about 10° to about 50°and preferably about 15° to 25° or approximately 21°. Additionally, thefrusto-conical region 238 is of a length greater than about 0.05 D1 and0.055 D2, preferably from about 0.1 D1 to 0.2 D1 and 0.15 D2 to 0.25 D2and more preferably approximately 0.15 D1 and 0.19 D2. Further,adjoining the first frusto-conical region 238 is the arcuate annularregion 240 which includes a radius of curvature in the range of 0.005 D1to 0.007 D1 and 0.007 D2 to 0.009 D2 and preferably approximately 0.006D1 and 0.008 D2 with the center point thereof being positioned adistance Y2 from the planar inner region 230. The included angle 242 ofthe arcuate annular region 240 may range from about 40° to about 92° andis preferably 65° to 87°. The second portion 244 of the arcuate annularregion 240, that is the distal portion of the arcuate annular region 240is positioned such that a line tangent to the curvature of the arcuateannular region 240 at the second portion 244 slopes downwardly andoutwardly at an angle of approximately 0° to 12°.

[0247] The combination of the annular region 234 and arcuate annularregion 240 should combine to position the second portion 244 of thearcuate annular region 240 in the manner set forth herein above. Thatis, the included angle 246 of the annular region 234 when combined withthe included angle 242 of the arcuate annular region 240 with the firstfrusto-conical region 248 spanning therebetween, positions the secondportion 244 of the arcuate annular region 240 in a manner such that thesecond frusto-conical region 250, which extends substantiallytangentially from the distal end of the second portion 244 of thearcuate annular region 240 extends outwardly and downwardly at an angleof about 0° to 12°. The second frusto-conical region 250 is of a lengthin a range from about 0.045 D1 to about 0.055 D1 and 0.030 D2 to about0.040 D2 and is preferably 0.052 D1 and 0.034 D2. Because the secondfrustoconical region 250 extends substantially tangentially from thesecond portion 244 of the arcuate annular region 240, the secondfrusto-conical 250 extends outwardly and downwardly at an angle A3 inthe range from approximately 0° to 12° with respect to a horizontalplane formed by the planar inner region 230.

[0248] Adjoining an outer periphery of the second frusto-conical region238 is the lip 252 which is in the form of yet another frusto-conicalregion which extends outwardly and downwardly from the secondfrusto-conical region 250. The lip 252 is of a length of at least 0.006D1 and 0.009 D2 and is preferably approximately 0.010 D1 and 0.013 D2.Further, the lip 252 extends at an angle A2 of no more than 45° fromvertical, preferably approximately 10 to 30° with respect to thevertical plane and more preferably approximately 20°.

[0249] At the transition between the second frusto-conical region 250and the lip 252 is a transition region 254. The transition region 254includes a radius of curvature R3 which is in the range of about 0.005D1 to 0.007 D1 and 0.007 D2 to 0.009 D2 and is preferably approximately0.006 D1 and 0.008 D2 with the center point thereof being positioned adistance Y3 from the planar inner region 230. Additionally, thetransition region 254 has an included angle A4 of approximately 48° to80°.

[0250] There is shown in FIGS. 25 through 28 still yet anotherembodiment of the inventive articles. Throughout the followingdescription of FIGS. 25 through 28, each of the dimensions arereferenced with respect to a given diameter D which, in accordance withthe present invention as illustrated in FIGS. 25 through 28, isapproximately 7.5 inches. However, the particular diameter of thecontainers is not a critical limitation and is only set forth herein byway of example. It is the relationship between the various portions ofthe rim configuration which are essential. The planar inner region 260in accordance with the illustrated embodiment in FIGS. 25 through 28,has a radius X1 which is equal to approximately 0.2 D to 0.3 D andpreferably 0.25 D. Adjoining an outer periphery of the planar innerregion 260 is a sidewall portion 262 including annular region 264 havinga radius of curvature equal to approximately 0.05 D to 0.15 D andpreferably 0.11 D with the center point thereof being positioned adistance Y1 from the planar inner region 260. Included angle 266 of theannular region 264 is from about 45° to about 75° and preferably about60° to 70° or approximately 65°. Adjoining the periphery of the annularregion 264 is the first frusto-conical region 268 which slopes upwardlyat an angle A1 with respect to the vertical from about 15° to about 45°and preferably about 20° to 30° or approximately 25°. Additionally, thefrusto-conical region 268 is of a length greater than about 0.1 Dpreferably from about 0.17 D to about 0.19 D and more preferablyapproximately 0.18 D. Further, adjoining the first frustro-conical isthe arcuate annular region 270 which includes a radius of curvature inthe range of 0.015 D to 0.030 D and preferably approximately 0.023 Dwith the center point thereof being positioned a distance Y2 from theplanar inner region 260. The included angle 272 of the arcuate annularregion 270 may range from about 45° to about 87° and is preferably 60°to 77°. The second portion 274 of the arcuate annular region 270, thatis the distal portion of the arcuate annular region 270 is positionedsuch that a line tangent to the curvature of the arcuate annular region270 at the second portion 274 slopes downwardly and outwardly at anangle of approximately 0° to 12°.

[0251] The combination of the annular region 264 and arcuate annularregion 270 should combine to position the second portion 274 of thearcuate annular region 260 in the manner set forth herein above. Thatis, the included angle 266 of the annular region 264 when combined withthe included angle 272 of the arcuate annular region 270 with the firstfrusto-conical region 264 spanning therebetween, positions the secondportion 274 of the arcuate annular region 270 in a manner such that thesecond frusto-conical region 276, which extends substantiallytangentially from the distal end of the second portion 274 of thearcuate annular region 270 extends outwardly and downwardly at an angleof about 0° to 12°. The second frusto-conical region 276 is of a lengthin a range from about 0.02 D to about 0.04 D and is preferably 0.03 D.Because the second frusto-conical region 276 extends substantiallytangentially from the second portion 274 of the arcuate annular region270, the second frusto-conical region 276 extends outwardly anddownwardly at an angle A3 in the range from approximately 0° to 12° withrespect to a horizontal plane formed by the planar inner region 260.

[0252] Adjoining an outer periphery of the second frusto-conical region268 is the lip 278 which is in the form of yet another frusto-conicalregion which extends outwardly and downwardly from the secondfrusto-conical region 276. The lip 278 is of a length of at least 0.01 Dand is preferably approximately 0.017 D. Further, the lip 278 extends atan angle A2 of no more than 45° from vertical, preferably approximately10° to 30° with respect to the vertical plane and more preferablyapproximately 25°.

[0253] At the transition between the second frusto-conical region 276and the lip 278 is a transition region 280. The transition region 280includes a radius of curvature R3 which is in the range of about 0.007 Dand 0.012 D and is preferably approximately 0.009 D with the centerpoint thereof being positioned a distance Y3 from the planar innerregion 260. Additionally, the transition region 280 has an includedangle A4 of approximately 48° to 80°.

[0254] There is shown in FIG. 29 yet another embodiment of a foodcontact article in accordance with the present invention. The containersof this invention may be formed as take-out containers, and arepresentative embodiment, a suitable take-out container, will now bedescribed in general with respect to FIG. 29 wherein the lid and basemay be formed as described in U.S. Pat. No. 5,377,860 which isincorporated herein by reference. While the container illustrated inFIG. 29 is oblong in configuration, the container may be round, oval,substantially rectangular or square as dictated by the contents whichare to be placed within the container. The container 290 is formed of abase or bottom portion 292 and a lid 294. The lid 294 includes radiallyextending opening tabs 296 which cooperate with the radially extendingopening tabs 298 of the base 292 in order to allow the consumer toreadily open the sealed container. The base 292 of the container 290includes a substantially planar bottom 300 and a substantiallyvertically extending peripheral sidewall 302. Integrally connected tothe upstanding sidewall 292 is a sealing brim 304 which is receivedwithin a cooperating sealing brim 306 of the lid 294.

[0255] The lid 294 includes a substantially planar top portion 308 and arim 310 extending about a periphery of the top portion 398. The rim 310is provided in order to enhance the strength of an extended volumeportion 312 of the lid 294. The rim 310 also serves to locate the base292 on the lid when the lid is used as a stand.

[0256] The extended volume portion 312 is formed by extension wall 314positioned about the perimeter of the rim 310 and extending downwardlytherefrom. The extension wall 314 is integrally formed with a horizontallid reinforcing ring 316 which is substantially parallel to the topportion 308 of the lid 294. The outer perimeter of the lid reinforcingring 316 is further integrally formed with the sealing brim 306. Also,extending radially outward from the sealing brim 306 is a secondhorizontal lid reinforcing ring 318 which extends substantially parallelto the top portion 308 as well.

[0257] Similarly, the base 292 includes a horizontal lid reinforcingring 320 which extends from the periphery of the sealing brim 304 foraiding in and maintaining the structural integrity of the sealing brim304 as well as the container 290 as a whole. In addition to thereinforcing ring 320, a step 322 may be provided about an upper portionof the peripheral sidewall 302 for preventing nested units from becomingjammed together due to excessive interpenetration when stacked andnested. Also, formed in an upper portion of the sidewall 302 areundercuts 324 which cooperate with detents 326, only one of which isillustrated in FIG. 29 at the integral connection between a brim 306 andlid reinforcing ring 316. The detents, when engaged in the undercuts324, provide an audible indication that the container is in fact sealed.Additionally, undercuts 328 may be provided in an outer periphery of thebrim 304 for receiving detents 330 formed in an outer portion of thebrim 306 for again providing an audible indication that the container issealed. While the container illustrated in FIG. 29 shows detents andundercuts formed in both the inner and outer portions of the brims 324and 306, respectively, it may be desired to provide respective detentsand undercuts on only one side of the brim or to provide no undercutsand detents on either side of the brim.

[0258] In a yet still further embodiment of this invention another bowlis illustrated in FIGS. 30 through 33. Throughout the followingdescription of the bowl of FIGS. 30 through 33, each of the dimensionsare referenced with respect to a given diameter D which, in accordancewith the present invention as illustrated is approximately 7.3 inches.However, the particular diameter of the containers is not a criticallimitation and is only set forth herein by way of example. It is therelationship between the various portions of the rim configuration whichare essential. The crowned inner region 340 in accordance with theillustrated embodiment in FIGS. 30 through 33, has a crown height Y5which is approximately 0.004 D to 0.012 D or preferably 0.008 D, andencompassing a radius X1 which is equal to approximately 0.2 D to 0.3 Dand preferably 0.25 D. Adjoining an outer periphery of the crowned innerregion 340 is a sidewall portion 342 including first annular region 344having a radius of curvature equal of approximately 0.05 D to 0.15 D andpreferably 0.11 D with the center point thereof being positioned atdistance Y1 from the tangency point between the crowned inner region 340and the first annular region 344. Included angle 346 of the firstannular region 344 is from about 45° to about 85° and is preferably 65°to 80° or approximately 72°. Adjoining the periphery of the firstannular region 344 in the sidewall portion 342 is a second annularregion 348 having a radius of curvature equal of approximately 0.8 D to1.2 D and preferably 0.96 D with the centerpoint thereof beingpositioned a distance Y2 from the tangency point between the crownedinner region 340 and the first annular region 344. The included angle ofarc A2 indicated generally at 350 of the second annular region 348 isfrom about 2° to 12° and is preferably 5° to 9° or approximately 7°.Adjoining the periphery of the second annular region 348 in the sidewallportion 342 is a third annular region 352 having a radius of curvatureequal to approximately 0.1 D to 0.2 D and preferably 0.15 D with thecenterpoint thereof being positioned a distance Y3 from the tangencypoint between the crowned inner region 340 and the first annular region344. Included angle 354 of the third annular region 352 is from about20° to 50° and is preferably 25° to 40° or approximately 33°. Adjoiningthe sidewall portion 342 is a flange portion 356 including a fourthannular region consisting of regions 358 and 360 which have the sameradius of curvature. Adjoining the third annular region 352 is a fourthannular region beginning with annular region 358 which extends to theuppermost bowl height and continuing with annular region 360 to bowldiameter D. Annular regions 358 and 360 are equivalent to one annularregion, flange portion 356 since both have the same radius of curvatureof approximately 0.02 D to 0.05 D and preferably 0.03 D with thecenterpoint thereof being positioned a distance Y4 from the tangencypoint between the crowned inner region 340 and the first annular region344. Included angle 362 of the fourth annular region 356 is from about45° to 85° and preferably 65° to 80° or approximately 73°.

[0259] Physical Properties, Heat Resistance and Food Contact Suitability

[0260]FIG. 34 shows rigidity versus current plate material costcomparisons for mica filled polypropylene plates versus competitorplastic disposable plates. “J” refers to mica filled polypropylene plateof this invention and “S” refers to polystyrene based plates such asthose currently manufactured by Solo Cup Company. Average plate calipersare indicated for each plate type and size. The left side of the diagramshows data for 8.75 inch plates whereby the J plate rigidity is aboutthree times higher than S at significantly reduced caliper and cost. Theright side of the diagram shows data for 10.25 inch plates whereby Jplated rigidity is more than seven times higher S at the same caliper.The open circle point corresponds to an estimated rigidity for the 10.25inch J plate that is scaled down in caliper so that plate material costsare equivalent to S.

[0261] The scaled J caliper X is calculated as X=(19 mil)(2.9 cents/3.8cents). The theoretical rigidity R1 at equivalent cost for thedownscaled caliper is calculated as:

(R1/R2)=(14.5 mil/19 mil) exp N

[0262] where R2 is the experimental rigidity at 19 mil and N=1.816 isthe caliper exponent value for the Dixie Superstrong 10.25 inch platedesign which is obtained from the general equation for rigidity:

R=(KE) TexpN

[0263] where E is Young's modulus, K is a shape constant, and T iscaliper. The data set forth in FIG. 34 demonstrate that the rigidity ofthe J plate of this invention is significantly higher at equivalent orlower material cost than commercial polystyrene polymer based plates.

[0264] In FIG. 35, the heat resistance performance for mica filledpolypropylene 10.25 inch plates (J), having an average caliper of 19 ml(J) is compared with (S) polystyrene based plates (S) of the same sizeand caliper. A measure of heat resistance is dynamic flexural storagemodulus E′, as measured with the Rheometrics Solids analyzer at 10rad/sec. Higher E′ values indicate increased stiffness and improveddimensional stability. Dynamic mechanical sprectroscopy is a commontechnique used for evaluation of viscoelastic properties of polymericmaterials with respect to temperature and input frequency (deformationtime scale). Dynamic mechanical properties of flat rectangular specimensof S plate material and PP/mica sheet of this invention were subjectedto flexural deformation at 10 rad/sec, using the Rheometrics SolidsAnalyzer RSAII instrument, manufactured by Rheometric Scientific, andequipped with a dual cantilever bending fixture. Temperature scans wereconducted at 0.05% strain using 2° C. temperature steps with a 0.5minute soak time at each temperature. From the time lag between inputstrain delivered by the driver motor and the stress output measured bythe transducer, values of material complex modulus E* are obtained. Theparameter E* is formally expressed as E*=E′+iE″, where E′ is the storagemodulus (purely elastic term) and E″ is the loss modulus (purely viscousterm). The storage modulus E′ is defined as the stress in phase with thestrain divided by the strain, which gives a measure of the energy storedand recovered per cycle. The loss modulus E″ is defined as the stress 90degrees out of phase with the strain divided by the strain, which givesa measure of the energy dissipated per cycle. The ratio of loss modulusto storage modulus is commonly known as the damping (tan delta) wheredelta is the phase angle between stress and strain. The dynamic storageflexural modulus E′ is the operative measure of heat resistanceperformance, where higher values mean higher performance. At ambientconditions (77° F.), E′ for mica filled polypropylene plates of thisinvention is appreciably higher than for S. At 250° F., whichcorresponds to aggressive temperatures which are commonly encountered inthe microwave heating or cooking of greasy foods, the heat resistance ofJ plates of this invention is significantly superior to the platesmanufactured by S, as further demonstrated below in connection withmicrowave cooking trials. TABLE 20 MICROWAVE COOKING TEST RESULTS FORPLATES J AND S PLATE TYPE FOOD TYPE J S Donut Pass Sugar glazing sticksBroccoli/cheese Pass Significantly deforms Pepperoni pizza Pass Moderatedeformation, Staining Barbecue pork Slight stain Significantstain/warpage Pancake/syrup Pass Significant warpage Beans & pork PassSignificant warpage Butter Slight warpage Significant warpage BaconModerate warpage Significant Localized melting, no leak warpage Rubberyplate flows and Sticks to glass tray

[0265] Microwaveability

[0266] Fort James Corporation (J) plate specimens of this invention andplates manufactured by Solo Cup Company (S) were tested in the microwave(Samsung model MW 8690) with a variety of foods. The highest powersetting (10) was used in all cases and cooking/heating times andprocedures corresponded to food manufacturer instructions on thepackages. Most tested foods were of the frozen microwaveable type andwere placed in a semi-thawed state directly on plates prior to cooking.When appropriate, a loose covering of wax paper was employed during thecooking process. After cooking, the plates were gently washed with warmwater and inspected. The following are the detailed test results whichare also summarized in above Table 20.

[0267] TEST #1 RESULTS - Sugar Glazed Donut

[0268] J A large, oval shaped sugar glazed plain donut was microwaved onthe plate of this invention for 60 seconds. The sugar glazing melted,bubbled, and flowed on the plate. The boiling sugar and grease mixturecaused the bottom of the plate to feel very warm but the plate exhibitedno warping, no staining, no softening, and no soak-through. The platewas cool enough to be safely handled. The residue of the donut waseasily washed off and the appearance of the used plate was excellent.

[0269] S The bottom of the plate got hot and slightly deformed with nosoak-through, however, sugar stuck to the plate.

[0270] TEST #2 RESULTS - Broccoli With Cheese Sauce

[0271] J Green Giant 10 oz. Broccoli with cheese sauce was removed fromthe flexible pouch and heated for five minutes in the microwave on theplate with loose covering of wax paper. The cheese melted and bubbled onthe plate without sticking. The plate bottom was warm, but nosoak-through and no loss of dimensional stability was observed. Afterwashing, no staining was observed and the appearance of the used platewas excellent.

[0272] S The plate bottom got hot and significantly deformed with nosoak-through.

[0273] TEST #3 RESULTS - Pepperoni pizza

[0274] J Tombstone 7 oz. Pepperoni pizza was cooked on an uncoveredplate for 4 minutes. The cheese melted and started bubbling abouthalfway through the test. The molten cheese mingled with the hot liquidfat extruded from the pepperoni and dripped on the sides of the crustonto the plate. No sticking, no soak-through, no staining, and no lossin plate dimensional stability was observed and the appearance of theused plate was excellent.

[0275] S The plate bottom got hot and moderately deformed with nosoak-through. The greasy reddish stain from oil in pepperoni could notbe completely washed off.

[0276] TEST #4 RESULTS - Microwave Kid Meal:

[0277] Pork Rib Patties, Barbecue Sauce, Fries, Honey Corn Bread

[0278] J A quick meal preparation simulation test was conducted using aSwanson 7.2 oz. microwave kids' meal with ingredients consisting ofpartially cooked boneless pork rib patties, barbecue sauce, fries, andhoney corn bread. The food was transferred from the compartmented trayonto the plate. Sauce was spooned on top of the pork meat and wasallowed to drip on the sides of the patties and onto the plate. Thecornbread batter was spooned out and was placed on the plate next to thefries. The food was loosely covered with wax paper and cooked for 3.5minutes. Examination after microwaving showed that the cornbread wasfully cooked and there was no sticking or damage to the plate. The friesand pork meat with sauce caused no soak-through and no loss in platedimensional stability. Washing of plate revealed the presence of slightstaining from barbecue sauce. Overall, the appearance of the used platewas very good.

[0279] S The plate bottom deformed mainly from pork meat withconsiderable staining from the barbecue sauce without soak-through.

[0280] TEST #5 RESULTS - Beans With Pork and Tomato Sauce

[0281] J Beans with pork and tomato sauce (8 oz. Can) were placed on theplate, covered with wax paper and heated for 2 minutes near boiling. Thebottom of plate got hot, but the rim was cool to touch. The hot platebottom exhibited no bulging and also, when the hot food plate washandled by the rim there was no perceived loss in dimensional stability.No soak-through, no warping and no staining was observed. The appearanceof the plate was excellent.

[0282] S The plate bottom became very hot and severely deformed with nosoak-through and when handled by the rim, the plate felt like it had lowrigidity.

[0283] TEST #6 RESULTS - Pancakes With Syrup and Precooked Bacon

[0284] J In this test, Swanson microwave pancakes and bacon breakfast(4.5 oz. size) were used. The semi-thawed meal consisted of threepancakes and three partially, precooked bacon strips. The pancakes andbacon were removed from the tray in carton and placed on plate.Approximately 5 teaspoons of pancake syrup was spooned over the pancakesand the assembled meal was covered with wax paper and microwaved for 2minutes. Although the bottom of the plate got hot, the overall plateperformance was excellent, i.e. no warpage, no soak-through, no loss indimensional stability, and no staining. Some hot grease was exuded bythe bacon during crisping but there was no observed damage to the plate.The appearance of the used plate was excellent.

[0285] S The plate bottom became hot and significantly deformed(especially in areas where bacon was placed), but no soak-through wasobserved and when handled by the rim, the plate felt soft.

[0286] TEST #7 - Butter

[0287] J Butter (5-tsp. chunk) was placed on the plate and was looselycovered with wax paper and was microwaved for 3 minutes. The buttermelted completely and covered the whole plate bottom. The butter beganboiling toward the end of the test. The plate bottom got very hot andbecame slightly warped but no soak-through. The rim of the plate feltcool to touch enabling safe removal of the plate from the microwaveoven. A small portion of the butter became charred but was easily washedoff the plate. Overall plate performance was good.

[0288] S The plate bottom became very hot and was significantly warpedbut no soak-through was observed and the greasy film residue could notbe washed off completely. Plate felt soft and rubbery when handled bythe rim.

[0289] TEST #8 RESULTS - Bacon

[0290] J Three strips of raw, cured bacon were wrapped in three sheetsof paper towel and cooked for 5 minutes. All of the bacon became crispyand about 20% of it was charred. The bottom of plate got very hot butmost of the rim area was relatively cool to the touch. Grease exudedfrom bacon and soaked through the towel. The grease pooled on the platebottom, side and on some rim areas. The grease which pooled in some rimregions caused localized melting of the plate but no holes were formed.The hot grease which pooled on plate bottom caused significant warpagebut no soak-through. Overall plate performance for Test #8 was lesssatisfactory than Test #7.

[0291] S When the raw bacon was wrapped in paper toweling and cooked onthe S plate, the bottom became very soft and stuck to the glass tray inthe microwave. Under such hot grease conditions, the adhering polymerregions underwent localized melting and stretched when the plate waslifted off the glass tray. The plate was severely warped but no holesformed and no soak-through was noticed.

[0292] With the possible exception of raw bacon, the behavior of the Jplate of this invention in the microwave oven is considered excellentwith a variety of aqueous, greasy/fatty, sugary food combinations. Nounusual or off odors were detected during and after cooking for eachtype of food directly on the plate. The foregoing data demonstrates thesuperior properties of the plates of this invention.

[0293] Crack Resistance

[0294] Low temperature crack resistance of rigid plates is of paramountimportance when considering that product must survive during storage andshipping to point of sale. Normally, it is difficult to improve crackresistance or reduce brittleness of rigid polymeric materials withoutreducing the stiffness which is usually the case when introducingexcessive amounts of softer extensible materials such as polyethylenes,rubber modified resins and the like. In order to be successful inimparting crack resistance without significantly reducing stiffness, onemust add relatively low amounts of polyethylene or rubber modifiedadditives, generally in the range of several to about 5 wt %. However,this invention shows that addition of low levels of polyethylene aloneis not sufficient to promote crack resistance whereby the desired resultis produced by a synergistic binary combination of polyethylene andTiO2. Such low odor products have high crack resistance which rendersthem useful in the commercial sense.

EXAMPLES 63 - 70

[0295] There is provided in a still further aspect of the inventiontoughened, crack resistant articles. It has been found thatpolypropylene/mica/polyethylene/titanium dioxide formulations without acoupling agent resist cracking. Generally, the articles have thecomponents set forth in Table 21, in the amounts mentioned above in thesummary of the invention herein. In Table 21, it is demonstrated thatpolyethylene/titanium dioxide exhibit synergy in resisting cracking.TABLE 21 Low Temperature crack data for 9 inch plates made of PP/30%mica/10% CaCO₃ modified with various combinations of TiO₂, polyethylene,or coupling agent Coupling TiO₂ LLDPE HDPE Agent Percent Cracked Example# (wt %) (wt %) (wt %) (wt %)* plates at 0 F** 63 — 4 — — 100 (n = 5) 64— — — 2.5 100 (n = 5) 65 1.9 — — — 100 (n = 5) 66 — 4 — 2.5 100 (n = 5)67 1.9 0 0 2.5 100 (n = 5) 68 0.5 4 — 2.5  60 (n = 5) 69 0.5 4 0 0  0 (n= 5) 70 0.5 0 4 0  0 (n = 10)

[0296] Crack resistance of Examples 63 through 70 was evaluated in thelaboratory according to method set forth below which was found useful asan investigative tool for optimizing the formulation with variouscombination of TiO2, polyethylene, or coupling agent. A laboratoryprocedure was devised and used to evaluate the crack resistance ofplates. Specifically, following is a description of test instruments andassociated fixtures used to subject plates to a repeatable rim crushingforce. The model numbers of standard equipment used on this procedureare recited below and additional fixtures used in these tests wereemployed as follows:

[0297] Instron - Model #55R402 was used which was equipped with InstronEnvironmental Chamber Model #3111. The Instron environmental chamber -Model 11 was modified to control low temperatures with liquid nitrogen.It was equipped with a control solenoid mounted on the rear of thecabinet and an electronic control module mounted on the control panelassembly. The temperature within the chamber was controlled inrelationship to the setpoint on the front panel temperature dial. Athermocouple within the chamber provides feed back to the device. Amercury thermometer was placed in the chamber and oriented so thattemperature within the chamber was visible through an insulated glassdoor. It was monitored and adjusted to 0° C. using the panel temperaturedial.

[0298] A push rod was attached to the load cell of the instron and waspassed through an opening in the top of the environmental chamber. Acircular metal device measuring 100 mm in diameter and 10 mm in thickwas attached to the end of the push rod inside the chamber. Thiscircular metal device was used to contact the edge of a plastic plateduring testing.

[0299] The plate support fixture was placed on a circular metal basesupport which measured 140 mm in diameter by 14 mm thick. This metalbase support was located just above the inside floor of theenvironmental chamber. It was attached to a support rod that passesthrough the floor of the environmental chamber and attached to the baseof the instron. Centering stops were provided on the metal base supportso that the plate support fixture could be repeatedly placed at the samelocation in the environmental cabinet.

[0300] The plate support fixture is constructed of 5-mm thick sheets ofplexiglas. The main base of this fixture measures 100×125 mm. The 125-mmdimension represents the width of the front of the mixture. The edge ofthe 125 mm side of a second plexiglas panel measuring 160×125 mm waspermanently attached to the plexiglas main base. This panel was attachedat a 90° angle to the main base and 35 mm in from the front edge. An Lshaped plexiglas component was attached to the main base behind andparallel to the permanent panel by thumbscrews. Two 20-mm long slotswere provided in the base of the L shaped component to allow attachmentand provide movement for adjustment to hold the test plate. The shortleg or base of the L shaped component faces the rear of the fixture. Ablock measuring 40×25×15 mm thick was permanently attached at the uppermost end at the center of the L shaped component. This block is locatedon the front side of the moveable component or just opposite the shortleg of the L shaped component, while an adjustable plate stop wasattached to one side of the moveable L shaped component.

[0301] The methodology for testing the crack resistance of plates was asfollows. The test plate was secured in a vertical position on edge inthe plate support fixture. The bottom of the test plate was placedagainst the permanently attached plexiglas panel of the plate supportfixture. The thumbscrews were loosened on the moveable portion of theplate support fixture. The L shaped moveable component was moved towardthe plate. The plate was held in a vertical position by the fixedplexiglas panel and the block which was attached to the wall of the Lshaped moveable component.

[0302] The plate stop located on the L shaped moveable component wasadjusted so that the center of the plate would align with the center ofthe plate support fixture. The plate support fixture along with the testplate secured in a vertical position was placed on the metal basesupport in the environmental chamber. The instron was adjusted so thatthe push rod crush assembly was located 0.5 inches above the plate edge.

[0303] Prior to the test, the environmental chamber was adjusted to 0°F. After placement of the plate support fixture along with the testplate secured in a vertical position in the environmental chamber, thechamber had to reestablish 0° F. This time period was about 30 seconds.After re-establishment of the test temperature, the plate wasconditioned for an additional five minutes prior to the test.

[0304] The crosshead speed of the instron was set at 40 inches perminute. After the five minute conditioning time period, the instron wasactivated and the edge crushing force applied. A set of five or a set often replicate plates was tested for each condition. The total number ofplates tested and the total number plates showing rim crack failure foreach condition tested are reported in Table 21. In addition, thepercentage of plates which cracked was calculated as shown above.

[0305] The above formulations for crack resistance testing werecompounded in the temperature range of 400 to about 425 F. on commercialBanbury equipment using batch sizes in the range of 150-200 lb andnominal mixing times of 3 min followed by underwater pelletizing.

[0306] Pellets were subsequently extruded at 370 F. as cast sheets inthe range of 18 mil. Sheet line conditions also included a screw RPMvalue of 100, a chill roll temperature of 130 F. Plates weresubsequently vacuum thermoformed using a female mold, trimmed, andthereafter tested for crack resistance.

[0307] Data on Examples 63 through 65 show that presence of TiO2,polyethylene, or coupling agent alone is not sufficient to promote crackresistance of plates comprised of PP/mica/CaCO3. In addition, data onExamples 66 and 67 show that binary combinations of polyethylene withcoupling agent or TiO2 with coupling agent are two cases which are alsonot sufficient for imparting crack resistance. Furthermore, the tertiarycombination of TiO2, polyethylene, and coupling agent (Example 68) alsodoes not impart sufficient crack resistance, as evidenced by themajority of samples which exhibit cracking. Rather, the useful additivepackages of this invention (Examples 69 and 70) comprises the binarysystem of polyethylene (either LLDPE or HDPE) with at least 0.5 wt% TiO2whereby crack resistance is excellent as evidenced by no crackedsamples.

EXAMPLES 71-78

[0308] Additional plates were fabricated in accordance with theforegoing procedures and compositions; crack testing results appear inTable 22 below TABLE 22 Crack Data and Physical Properties for VariousCompounded Formulations Base Formulation: PP/30% Mica/10% CaCO₃ FlexuralFormulation Melt Flow Filler Modulus 9″ Plate Product Crack Data TiO₂ PECoupling g/10 min. Content Tangent Rigidity Weight @ 0° F. Example (wt.%) (4 wt. %) Agent* @ 230° C. (Wt. %) (psi) (grams/0.5″) (grams)(#Cracked Total) 71 0 LLDPE No 1.45 39.4 505,000 288 19.3 5/5 72 1.9LLDPE No 1.64 40.6 581,600 422 23.13 0/5 73 1.2 LLDPE No 2.05 39.8578,500 385 22.12 0/5 74 0.5 LLDPE No 1.77 38.6 487,500 286 20.65 0/5 751.9 HDPE No 1.5 40.6 637,500 436 22.70 1/5 76 1.9 0 Yes 1.9 39.0 717,585417 21.25 5/5 77 1.9 LLDPE Yes 1.6 39.6 494,000 391 21.6 5/5 78 1.9 0Yes 1.2 40.3 593,000 353 20.8 5/5

1. A microwaveable, disposable food contact article having food contactcompatible olfactory properties formed from a melt-processedpolyolefin/mica composition wherein said composition includes from about40 to about 90 percent by weight of a polypropylene polymer and fromabout 10 to about 50 percent by weight mica and wherein said meltprocessed composition exhibits a relative aroma intensity index of lessthan about 1.6.
 2. The microwaveable article according to claim 1 ,wherein said melt-processed composition further includes a basic organicor inorganic compound comprising the reaction product of an alkali metalor alkaline earth element with carbonates, phosphates, carboxylic acidsas well as alkali metal and alkaline earth element oxides, hydroxides,or silicates and basic metal oxides, including mixtures of siliconedioxide with one or more of the following oxides: magnesium oxide,calcium oxide, barium oxide, and mixtures thereof.
 3. The microwaveablearticle according to claim 2 , wherein the basic organic or inorganiccompound is selected from the group consisting of calcium carbonate,sodium carbonate, potassium carbonate, barium carbonate, aluminum oxide,sodium silicate, sodium borosilicate, magnesium oxide, strontium oxide,barium oxide, zeolites, sodium citrate, potassium citrate, sodiumcitrate, calcium stearate, potassium stearate, sodium phosphate,potassium phosphate, magnesium phosphate, mixtures of silicon dioxidewith one or more of the following oxides: magnesium oxide, calciumoxide, barium oxide, and mixtures of one or more of the above.
 4. Themicrowaveable article according to claim 3 , wherein the basic inorganiccompound is selected from the group consisting of calcium carbonate,sodium carbonate, potassium carbonate, barium carbonate, aluminum oxide,sodium silicate, sodium borosilicate, magnesium oxide, strontium oxide,barium oxide, zeolites, sodium phosphate, potassium phosphate, magnesiumphosphate, mixtures of silicone dioxide with one or more of thefollowing oxides: magnesium oxide, calcium oxide, barium oxide, andmixtures of one or more of the basic inorganic compounds set forthabove, wherein the amount of the basic inorganic compound is from about2 to about 20 weight percent of said article.
 5. The microwaveablearticle according to claim 4 , wherein said basic inorganic compound iscalcium carbonate.
 6. The microwaveable article according to claim 5 ,wherein calcium carbonate is present in said article from about 5 toabout 20 weight percent.
 7. The microwaveable article according to claim3 , wherein said basic organic compound is selected from the groupconsisting of sodium stearate, calcium stearate, potassium stearate,sodium citrate, potassium citrate, and mixtures of these wherein theamount of the basic organic compound is from about 0.5 to about 2.5weight percent of said article.
 8. The microwaveable article accordingto claim 1 , wherein said composition exhibits a relative aromaintensity index of less than about 1.0.
 9. The microwaveable articleaccording to claim 8 , wherein said composition exhibits a relativearoma intensity index of less than about 0.7.
 10. The microwaveablearticle according to claim 1 , wherein said article is a bowl or aplate.
 11. The microwaveable article according to claim 1 , wherein saidarticle is produced by injection molding.
 12. The microwaveable articleaccording to claim 1 , wherein said article is thermoformed from a sheetmade from melt-extruded polypropylene/mica pellets.
 13. The articleaccording to claim 12 , wherein said article is formed, thermoformed,vacuum thermoformed by application of pressure, thermoformed byapplication of vacuum, or thermoformed by a combination of vacuum andpressure, into the shape of a container; said container exhibiting amelting point of no less than about 250° F., said container beingdimensionally stable and resistant to grease, sugar and water attemperatures up to at least 220° F. and of sufficient toughness to beresistant to cutting by serrated polystyrene flatware.
 14. Themicrowaveable article according to claim 12 , wherein said article hasat least one micronodular food contact surface.
 15. The microwaveablearticle according to claim 14 , wherein said micronodular surface isproduced through vacuum thermoforming on the side opposite saidmicronodular food contact surface.
 16. The microwaveable articleaccording to claim 14 , wherein said micronodular food contact surfaceexhibits a surface gloss of less than about 35 at 75° as measured byTAPPI method T-480-OM
 92. 17. The microwaveable article according toclaim 16 , wherein said micronodular food contact surface exhibits aParker Roughness Value of at least about 12 microns.
 18. Themicrowaveable article according to claim 1 , wherein said polypropylenepolymer is selected from the group consisting of: isotacticpolypropylene, co-polymers of propylene and ethylene wherein theethylene moiey is less than about 10 percent of the units making up thepolymer and mixtures thereof.
 19. The microwaveable article according toclaim 18 , wherein said polymer is isotactic polypropylene and has amelt-flow index from about 0.3 to about
 4. 20. The microwaveable articleaccording to claim 19 , wherein said polypropylene has a melt flow indexof about 1.5.
 21. The microwaveable article according to claim 1 ,wherein said composition further includes a polyethylene component. 22.The microwaveable article according to claim 21 , wherein saidpolyethylene is selected from the group consisting of HDPE, LDPE, LLDPE,MDPE and mixtures thereof.
 23. The microwaveable article according toclaim 21 wherein said polyethylene component comprises HDPE.
 24. Themicrowaveable article according to claim 21 , wherein said polyethylenecomponent comprises LLDPE.
 25. The microwaveable article according toclaim 21 , further including titanium dioxide.
 26. The microwaveablearticle according to claim 1 , wherein said article exhibits a meltingpoint of from about 250 to about 330° F.
 27. The microwaveable articleaccording to claim 1 , wherein mica is present in said melt-processedcomposition from about 20 to about 35 weight percent.
 28. Themicrowaveable article according to claim 27 , wherein mica is present insaid melt-processed composition at about 30 weight percent.
 29. Themicrowaveable article according to claim 1 , wherein said article issubstantially free from volatile C8 and C9 organic ketones.
 30. Themicrowaveable article according to claim 1 , wherein said article isprepared from a melt compounded polyolefin/mica composition which isproduced at a process melt temperature of less than about 425° F. 31.The microwaveable article according to claim 30 , wherein said articleis produced from a melt compounded polyolefin/mica composition which isprepared at a temperature below about 400° F.
 32. The microwaveablearticle according to claim 30 , wherein said article is thermoformedfrom an extruded sheet produced from a melt compounded polyolefin/micacomposition which was prepared at a process melt temperature of lessthan about 425° F.
 33. The microwaveable article according to claim 1 ,wherein said melt processed polyolefin/mica composition is meltcompounded in a nitrogen atmosphere.
 34. The article of manufactureaccording to claim 1 , in the form of a plate having a substantiallyplanar center portion; a first rim portion extending outwardlytherefrom, said first rim portion being upwardly convex and subtending afirst arc with a first radius of curvature; a second rim portion joinedto said first rim portion, and extending outwardly therefrom, saidsecond rim portion being downwardly convex, subtending a second arc witha second radius of curvature; a third rim portion joined to said secondrim portion and extending outwardly therefrom, said third rim portionbeing downwardly convex, subtending a third arc with a third radius ofcurvature as well as a tangent thereto which is substantially parallelto the plane of said substantially planar center section; and, a fourthrim portion joined to said third rim portion and extending outwardlytherefrom, said fourth rim portion being downwardly convex subtending afourth arc having a fourth radius of curvature, wherein the length ofsaid second arc of said second rim portion is substantially less thanthe length of said fourth arc of said fourth rim portion which, in turn,is substantially less than the length of said first arc of said firstrim portion and wherein said fourth radius of curvature of said fourthrim portion is less than said third radius of curvature of said thirdrim portion which, in turn, is less than said second radius of curvatureof said second rim portion and wherein the angle of said first arc isgreater that about 55 degrees and the angle of said third arc is greaterthan about 45 degrees.
 35. The plate according to claim 34 , wherein theangle of said fourth arc is less than about 75 degrees.
 36. The plateaccording to claim 34 , wherein the length of said first arc issubstantially equivalent to the length of said third arc and said firstradius of curvature of said first arc is substantially equivalent tosaid third radius of curvature of said third arc.
 37. The plateaccording to claim 34 , wherein the height of the center of curvature ofsaid first rim portion above the plane of said substantially planarportion is substantially less than the distance by which the center ofcurvature of said second rim portion is below the plane of saidsubstantially planar portion.
 38. The plate according to claim 34 ,wherein the horizontal displacement of the center of curvature of saidsecond rim portion from the center of curvature of said first rimportion is at least about twice said first radius of curvature of saidfirst rim portion.
 39. The plate according to claim 34 , wherein saidheight of the center of curvature of said third rim portion above theplane of said substantially planar portion is less than the height ofthe center of curvature of said fourth rim portion above the plane ofsaid substantially planar portion.
 40. The plate according to claim 34 ,wherein the horizontal displacement of the center of curvature of saidsecond rim portion is located outwardly from the center of curvature ofboth said third and fourth rim portions.
 41. The plate according toclaim 34 , wherein the height of the center of curvature of said thirdrim portion above the plane of said substantially planar portion is lessthan about 0.75 times the radius of curvature of said fourth rim portionand the height of the center of curvature of said fourth rim portionabove the plane of said substantially planar portion is at least about0.4 times said first radius of curvature of said first rim portion. 42.A microwaveable, disposable food contact article having food contactcompatible olfactory properties formed of a melt-processedpolyolefin/mica composition wherein said composition includes from about40 to about 90 percent by weight of a polypropylene polymer and fromabout 10 to about 50 percent by weight mica and a basic organic orinorganic compound comprising the reaction product of an alkali metal oralkaline earth element with carbonates, phosphates, carboxylic acids aswell as alkali metal and alkaline earth element oxides, hydroxides orsilicates and basic metal oxides, including mixtures of silicone dioxidewith one or more of the following oxides: magnesium oxide, calciumoxide, barium oxide, and mixtures thereof.
 43. The microwaveable articleaccording to claim 42 , wherein the basic organic or inorganic compoundis selected from the group consisting of calcium carbonate, sodiumcarbonate, potassium carbonate, barium carbonate, aluminum oxide, sodiumsilicate, sodium borosilicate, magnesium oxide, strontium oxide, bariumoxide, zeolites, sodium citrate, potassium citrate, calcium stearate,potassium stearate, sodium phosphate, potassium phosphate, magnesiumphosphate, mixtures of silicon dioxide with one or more of the followingoxides: magnesium oxide, calcium oxide, barium oxide, and mixtures ofone or more of the above.
 44. The microwaveable article according toclaim 43 , wherein the basic inorganic compound is selected from thegroup consisting of calcium carbonate, sodium carbonate, potassiumcarbonate, barium carbonate, aluminum oxide, sodium silicate, sodiumborosilicate, magnesium oxide, strontium oxide, barium oxide, zeolites,sodium phosphate, potassium phosphate, magnesium phosphate, mixtures ofsilicone dioxide with one or more of the following oxides: magnesiumoxide, calcium oxide, barium oxide, and mixtures of one or more of thebasic inorganic compounds set forth above, wherein the amount of thebasic inorganic compound is from about 5 to about 20 weight percent ofsaid article.
 45. The microwaveable article according to claim 44 ,wherein said basic inorganic compound is calcium carbonate.
 46. Themicrowaveable article according to claim 45 , wherein calcium carbonateis present in said article from about 8 to about 12 weight percent. 47.The microwaveable article according to claim 42 , wherein said basicorganic compound is selected from the group consisting of sodiumstearate, calcium stearate, potassium stearate, sodium citrate,potassium citrate, and mixtures of these wherein the amount of the basicorganic compound is from about 0.5 to about 2.5 weight percent of saidarticle.
 48. A low temperature compounding process for preparingpolypropylene/mica melt compounded product which includes a basicodor-suppressing agent having olfactory properties suitable for foodcontact applications comprising the sequential steps of: (a) preheatinga polypropylene polymer while maintaining the polymer below a maximumtemperature of about 350° F.; followed by (b) admixing mica to saidpre-heated polymer in an amount from about 10 to about 50 percent byweight based on the combined weight of resin and mica; followed by (c)extruding said mixture.
 49. The process according to claim 48 , whereinsaid maximum temperature of Step (a) is about 260° F.
 50. The processaccording to claim 48 , wherein said polymer is melted through theapplication of shear.
 51. The process according to claim 48 , whereinsaid polypropylene polymer is preheated prior to said admixing stepexternally to the vessel in which said step of admixing the mica takesplace.
 52. The process according to claim 48 , wherein the duration ofStep (b) is a maximum of about 5 minutes.
 53. The process according toclaim 48 , wherein the duration of Step (b) is a maximum of about 3minutes.
 54. The process according to claim 48 , wherein said basic odorsuppressing agent is added to the mixture simultaneously with said micain step (b) of the process.
 55. The process according to claim 54 ,wherein said steps of preheating said polymer and admixing said mica andodor suppressing compound to said resin are carried out in a batch modein a mixing chamber provided with a pair of rotating rotors.
 56. Theprocess according to claim 48 , wherein said odor suppressing compoundis a basic organic or inorganic compound comprising the reaction productof an alkali metal or an alkaline earth element with carbonates,phosphates, carboxylic acids, as well as alkali metal and alkaline earthelement oxides, hydroxides or silicates, basic metal oxides includingmixtures of silicon dioxide with one or more of the following oxides:magnesium oxide, calcium oxide, barium oxide, and mixtures of one ormore of the organic or inorganic compounds set forth above.
 57. Theprocess according to claim 56 , wherein the basic organic or inorganiccompound is selected from the group consisting of calcium carbonate,sodium carbonate, potassium carbonate, barium carbonate, aluminum oxide,sodium silicate, sodium borosilicate, magnesium oxide, strontium oxide,barium oxide, zeolites, sodium citrate, potassium citrate, sodiumstearate, calcium stearate, potassium stearate, sodium phosphate,potassium phosphate, magnesium phosphate, mixtures of silicone dioxidewith one or more of the following oxides: magnesium oxide, calciumoxide, barium oxide, and mixtures of one or more of the organic orinorganic compounds set forth above.
 58. The process according to claim57 , wherein the basic inorganic compound is selected from a groupconsisting of calcium carbonate, sodium carbonate, potassium carbonate,barium carbonate, aluminum oxide, sodium silicate, sodium borosilicate,magnesium oxide, strontium oxide, barium oxide, zeolites, sodiumphosphate, potassium phosphate, magnesium phosphate, mixtures ofsilicone dioxide with one or more of the following oxides: magnesiumoxide, calcium oxide, barium oxide, and mixtures of one or more of thebasic inorganic compounds set forth above and wherein the amount of thebasic inorganic compound is from about 5 to about 20 weight percent ofthe composition.
 59. A process for forming a microwaveable, disposable,rigid and strong, mica and basic inorganic or organic compound filledpolyolefin container having food contact compatible olfactoryproperties, said polyolefin being selected from the group consisting ofpolypropylene and polypropylene polyethylene copolymer or blend, and amixture of these wherein the inorganic or organic compound is selectedfrom the group consisting of calcium carbonate, sodium carbonate,potassium carbonate, barium carbonate, aluminum oxide, sodium silicate,sodium borosilicate, magnesium oxide, strontium oxide, barium oxide,zeolites, sodium phosphate, potassium phosphate, magnesium phosphate,sodium stearate, calcium stearate, potassium stearate, sodium citrate,potassium citrate, hydroxides of these elements, and mixtures of theseorganic compounds, mixtures of silicon dioxide with one or more of thefollowing oxides: magnesium oxide, calcium oxide, barium oxide, andmixtures of one or more of the basic inorganic or organic compounds setforth herein, comprising the steps of: (a) forming an extrudableadmixture of the polyolefin resin, mica, and the basic inorganiccompound or basic organic compound; (b) extruding said extrudableadmixture of the polyolefin resin, mica, and the basic inorganiccompound or the basic organic compound at elevated temperature; (c)passing the resulting extruded admixture of the polyolefin resin andmica and the basic inorganic compound or the basic organic compoundthrough a multiple roll stack, at least one roll of said stack having amatte finish; (d) thermoforming said extruded admixture of thepolyolefin, resin, mica, and the basic inorganic compound or organiccompound; and (e) recovering a container having a micronodular surfaceand exhibiting a melting point of no less than 250° F., said containerbeing dimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and having sufficient toughness to beresistant to cutting by serrated flatware wherein the amount of thebasic inorganic compound or basic organic compound added is sufficientto reduce carbonyl moiety containing decomposition products to providecontainers with suitable food contact compatible olfactory properties.60. A process for forming a microwaveable, disposable, rigid and strong,mica and basic inorganic or organic compound filled polyolefin containerhaving food contact compatible olfactory properties, said polyolefinbeing selected from the group consisting of polypropylene andpolypropylene polyethylene copolymer or blend, and a mixture of thesewherein the inorganic or organic compound is selected from the groupconsisting of calcium carbonate, sodium carbonate, potassium carbonate,barium carbonate, aluminum oxide, sodium silicate, sodium borosilicate,magnesium oxide, strontium oxide, barium oxide, zeolites, sodiumphosphate, potassium phosphate, magnesium phosphate, sodium stearate,calcium stearate, potassium stearate, sodium citrate, potassium citrate,corresponding hydroxides of the foregoing elements and mixtures of theseorganic compounds, mixtures of silicon dioxide with one or more of thefollowing oxides: magnesium oxide, calcium oxide, barium oxide, andmixtures of one or more of the basic inorganic or organic compounds setforth herein, comprising the steps of: (a) forming an extrudableadmixture of the polyolefin resin, mica, and the basic inorganiccompound or basic organic compound; (b) extruding said extrudableadmixture of the polyolefin resin, mica and the basic inorganic compoundor the basic organic compound at elevated temperature; (c) passing theresulting extruded admixture of the polyolefin resin and mica and thebasic inorganic compound or the basic organic compound through amultiple roll stack, at least one roll of said stack having a mattefinish; (d) passing said extruded admixture of the polyolefin resin,mica, and basic inorganic compound or the basic organic compound atleast partially around said roll having a matte finish; (e) controllingthe speed of said extrusion process, the size, temperature andconfiguration of said roll stack such that the surface of said extrudedadmixture of the polyolefin resin, mica, and the basic inorganic ororganic compound not in contact with said matte roll has acoarse-grained structure; (f) thermoforming said extruded admixture ofthe polyolefin, resin, mica, and the basic inorganic compound or organiccompound; and (g) recovering a container having a micronodular surfaceand a rough surface and exhibiting a melting point of no less than 250°F., said container being dimensionally stable and resistant to grease,sugar, and water at temperatures up to about 220° F. and havingsufficient toughness to be resistant to cutting by serrated flatwarewherein the amount of the basic inorganic compound or basic organiccompound added is sufficient to reduce carbonyl moiety containingdecomposition products associated with odor to provide containers withsuitable food contact compatible olfactory properties.
 61. The processof claim 60 wherein the coarse-grained structure of the surface of saidextruded admixture of the polyolefin resin, mica, and the basicinorganic compound or basic organic compound not in contact with saidmatte roll is formed by transversing the extruded admixture of thepolyolefin resin, mica, and the basic inorganic compound or basicorganic compound through a curvilinear path and at least partiallysolidifying the surface of said extruded admixture of polyolefin resin,mica, and the basic inorganic compound or basic organic compound notcontacting said matte roll while that surface is in tension relative tothe surface contacting said matte roll.
 62. The process of claim 60wherein the container is a plate.
 63. The process of claim 60 whereinthe container is a cup.
 64. The process of claim 60 wherein thecontainer is a bowl.
 65. The process of claim 60 wherein the containeris a tray.
 66. The process of claim 60 wherein the container is a lid.67. The process of claim 60 wherein the container is a compartmentedtray.
 68. The process of claim 60 wherein the container is a bucket. 69.The process of claim 60 wherein the container is a souffle dish.
 70. Acrack-resistant, thermoformed food contact article having a wallthickness from about 10 to about 80 mils consisting essentially of fromabout 40 to about 90 percent by weight of a polypropylene polymer, fromabout 10 to about 50 percent by weight mica, from about 1 to about 15percent by weight polyethylene, from about 0.1 to about 5 weight percenttitanium dioxide and optionally including a basic organic or inorganiccompound comprising the reaction product of an alkali metal or alkalineearth element with carbonates, phosphates, carboxylic acids as well asalkali metal and alkaline earth element oxides, hydroxides, or silicatesand basic metal oxides, including mixtures of silicone dioxide with oneor more of the following oxides: magnesium oxide, calcium oxide, bariumoxide, and mixtures thereof.
 71. The crack-resistant, thermoformed foodcontact article according to claim 70 , wherein said basic organic orinorganic compound comprises calcium carbonate and said calciumcarbonate is present in an amount of from about 5 to about 20 weightpercent
 72. The crack-resistant, thermoformed food contact articleaccording to claim 70 wherein polyethylene is present from about 2.5 toabout 15 percent by weight.
 73. The crack-resistant, thermoformed foodcontact article according to claim 72 , wherein polyethylene is presentfrom about 4 to about 5 weight percent.
 74. The crack-resistant,thermoformed food contact article according to claim 70 , whereintitanium dioxide is present from about 0.1 to about 3 weight percent.75. The crack-resistant, thermoformed food contact article according toclaim 74 , wherein titanium dioxide is present from about 0.25 to about2 percent by weight.
 76. The crack-resistant, thermoformed food contactarticle according to claim 70 wherein titanium dioxide is present in anamount of at least about 0.5 percent by weight.
 77. The crack-resistant,thermoformed food contact article according to claim 70 , wherein saidarticle has a wall caliper of from about 10 to about 50 mils.
 78. Thecrack-resistant, thermoformed food contact article according to claim 77, wherein said article has a wall caliper of from about 15 to about 25mils.
 79. The crack-resistant, thermoformed food contact articleaccording to claim 70 , wherein said mica is an untreated mica.
 80. Thecrack-resistant, thermoformed food contact article according to claim 70, wherein said polypropylene polymer is isotactic polypropylene.
 81. Thecrack-resistant, thermoformed food contact article according to claim 80, wherein said isotactic polypropylene has a melt index of from about0.3 to about
 4. 82. The crack-resistant, thermoformed food contactarticle according to claim 81 , wherein said isotactic polypropylene hasa melt flow index of about 1.5.
 83. The crack-resistant, thermoformedfood contact article according to claim 70 , wherein said polyethyleneis HDPE.
 84. The crack-resistant, thermoformed article according toclaim 70 , wherein said polyethylene is LLDPE.